i18n: git-branch "Deleted branch [...]" message
[gitweb.git] / unpack-trees.c
index dd5999c3562219b7993420b22257f4088ab82b8d..b68ec820dde935eb2578a8983c265290d0511add 100644 (file)
  * Error messages expected by scripts out of plumbing commands such as
  * read-tree.  Non-scripted Porcelain is not required to use these messages
  * and in fact are encouraged to reword them to better suit their particular
- * situation better.  See how "git checkout" replaces not_uptodate_file to
- * explain why it does not allow switching between branches when you have
- * local changes, for example.
+ * situation better.  See how "git checkout" and "git merge" replaces
+ * them using setup_unpack_trees_porcelain(), for example.
  */
-static struct unpack_trees_error_msgs unpack_plumbing_errors = {
-       /* would_overwrite */
+const char *unpack_plumbing_errors[NB_UNPACK_TREES_ERROR_TYPES] = {
+       /* ERROR_WOULD_OVERWRITE */
        "Entry '%s' would be overwritten by merge. Cannot merge.",
 
-       /* not_uptodate_file */
+       /* ERROR_NOT_UPTODATE_FILE */
        "Entry '%s' not uptodate. Cannot merge.",
 
-       /* not_uptodate_dir */
+       /* ERROR_NOT_UPTODATE_DIR */
        "Updating '%s' would lose untracked files in it",
 
-       /* would_lose_untracked */
-       "Untracked working tree file '%s' would be %s by merge.",
+       /* ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN */
+       "Untracked working tree file '%s' would be overwritten by merge.",
 
-       /* bind_overlap */
+       /* ERROR_WOULD_LOSE_UNTRACKED_REMOVED */
+       "Untracked working tree file '%s' would be removed by merge.",
+
+       /* ERROR_BIND_OVERLAP */
        "Entry '%s' overlaps with '%s'.  Cannot bind.",
+
+       /* ERROR_SPARSE_NOT_UPTODATE_FILE */
+       "Entry '%s' not uptodate. Cannot update sparse checkout.",
+
+       /* ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN */
+       "Working tree file '%s' would be overwritten by sparse checkout update.",
+
+       /* ERROR_WOULD_LOSE_ORPHANED_REMOVED */
+       "Working tree file '%s' would be removed by sparse checkout update.",
 };
 
-#define ERRORMSG(o,fld) \
-       ( ((o) && (o)->msgs.fld) \
-       ? ((o)->msgs.fld) \
-       : (unpack_plumbing_errors.fld) )
+#define ERRORMSG(o,type) \
+       ( ((o) && (o)->msgs[(type)]) \
+         ? ((o)->msgs[(type)])      \
+         : (unpack_plumbing_errors[(type)]) )
+
+void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
+                                 const char *cmd)
+{
+       int i;
+       const char **msgs = opts->msgs;
+       const char *msg;
+       char *tmp;
+       const char *cmd2 = strcmp(cmd, "checkout") ? cmd : "switch branches";
+       if (advice_commit_before_merge)
+               msg = "Your local changes to the following files would be overwritten by %s:\n%%s"
+                       "Please, commit your changes or stash them before you can %s.";
+       else
+               msg = "Your local changes to the following files would be overwritten by %s:\n%%s";
+       tmp = xmalloc(strlen(msg) + strlen(cmd) + strlen(cmd2) - 2);
+       sprintf(tmp, msg, cmd, cmd2);
+       msgs[ERROR_WOULD_OVERWRITE] = tmp;
+       msgs[ERROR_NOT_UPTODATE_FILE] = tmp;
+
+       msgs[ERROR_NOT_UPTODATE_DIR] =
+               "Updating the following directories would lose untracked files in it:\n%s";
+
+       if (advice_commit_before_merge)
+               msg = "The following untracked working tree files would be %s by %s:\n%%s"
+                       "Please move or remove them before you can %s.";
+       else
+               msg = "The following untracked working tree files would be %s by %s:\n%%s";
+       tmp = xmalloc(strlen(msg) + strlen(cmd) + strlen("removed") + strlen(cmd2) - 4);
+       sprintf(tmp, msg, "removed", cmd, cmd2);
+       msgs[ERROR_WOULD_LOSE_UNTRACKED_REMOVED] = tmp;
+       tmp = xmalloc(strlen(msg) + strlen(cmd) + strlen("overwritten") + strlen(cmd2) - 4);
+       sprintf(tmp, msg, "overwritten", cmd, cmd2);
+       msgs[ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN] = tmp;
+
+       /*
+        * Special case: ERROR_BIND_OVERLAP refers to a pair of paths, we
+        * cannot easily display it as a list.
+        */
+       msgs[ERROR_BIND_OVERLAP] = "Entry '%s' overlaps with '%s'.  Cannot bind.";
+
+       msgs[ERROR_SPARSE_NOT_UPTODATE_FILE] =
+               "Cannot update sparse checkout: the following entries are not up-to-date:\n%s";
+       msgs[ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN] =
+               "The following Working tree files would be overwritten by sparse checkout update:\n%s";
+       msgs[ERROR_WOULD_LOSE_ORPHANED_REMOVED] =
+               "The following Working tree files would be removed by sparse checkout update:\n%s";
+
+       opts->show_all_errors = 1;
+       /* rejected paths may not have a static buffer */
+       for (i = 0; i < ARRAY_SIZE(opts->unpack_rejects); i++)
+               opts->unpack_rejects[i].strdup_strings = 1;
+}
 
 static void add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
        unsigned int set, unsigned int clear)
@@ -47,21 +110,67 @@ static void add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
 
        clear |= CE_HASHED | CE_UNHASHED;
 
+       if (set & CE_REMOVE)
+               set |= CE_WT_REMOVE;
+
        memcpy(new, ce, size);
        new->next = NULL;
        new->ce_flags = (new->ce_flags & ~clear) | set;
        add_index_entry(&o->result, new, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 }
 
+/*
+ * add error messages on path <path>
+ * corresponding to the type <e> with the message <msg>
+ * indicating if it should be display in porcelain or not
+ */
+static int add_rejected_path(struct unpack_trees_options *o,
+                            enum unpack_trees_error_types e,
+                            const char *path)
+{
+       if (!o->show_all_errors)
+               return error(ERRORMSG(o, e), path);
+
+       /*
+        * Otherwise, insert in a list for future display by
+        * display_error_msgs()
+        */
+       string_list_append(&o->unpack_rejects[e], path);
+       return -1;
+}
+
+/*
+ * display all the error messages stored in a nice way
+ */
+static void display_error_msgs(struct unpack_trees_options *o)
+{
+       int e, i;
+       int something_displayed = 0;
+       for (e = 0; e < NB_UNPACK_TREES_ERROR_TYPES; e++) {
+               struct string_list *rejects = &o->unpack_rejects[e];
+               if (rejects->nr > 0) {
+                       struct strbuf path = STRBUF_INIT;
+                       something_displayed = 1;
+                       for (i = 0; i < rejects->nr; i++)
+                               strbuf_addf(&path, "\t%s\n", rejects->items[i].string);
+                       error(ERRORMSG(o, e), path.buf);
+                       strbuf_release(&path);
+               }
+               string_list_clear(rejects, 0);
+       }
+       if (something_displayed)
+               printf("Aborting\n");
+}
+
 /*
  * Unlink the last component and schedule the leading directories for
  * removal, such that empty directories get removed.
  */
 static void unlink_entry(struct cache_entry *ce)
 {
-       if (has_symlink_or_noent_leading_path(ce->name, ce_namelen(ce)))
+       if (!check_leading_path(ce->name, ce_namelen(ce)))
                return;
-       if (unlink_or_warn(ce->name))
+       if (remove_or_warn(ce->ce_mode, ce->name))
                return;
        schedule_dir_for_removal(ce->name, ce_namelen(ce));
 }
@@ -78,7 +187,7 @@ static int check_updates(struct unpack_trees_options *o)
        if (o->update && o->verbose_update) {
                for (total = cnt = 0; cnt < index->cache_nr; cnt++) {
                        struct cache_entry *ce = index->cache[cnt];
-                       if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
+                       if (ce->ce_flags & (CE_UPDATE | CE_WT_REMOVE))
                                total++;
                }
 
@@ -92,10 +201,11 @@ static int check_updates(struct unpack_trees_options *o)
        for (i = 0; i < index->cache_nr; i++) {
                struct cache_entry *ce = index->cache[i];
 
-               if (ce->ce_flags & CE_REMOVE) {
+               if (ce->ce_flags & CE_WT_REMOVE) {
                        display_progress(progress, ++cnt);
                        if (o->update)
                                unlink_entry(ce);
+                       continue;
                }
        }
        remove_marked_cache_entries(&o->result);
@@ -118,6 +228,62 @@ static int check_updates(struct unpack_trees_options *o)
        return errs != 0;
 }
 
+static int verify_uptodate_sparse(struct cache_entry *ce, struct unpack_trees_options *o);
+static int verify_absent_sparse(struct cache_entry *ce, enum unpack_trees_error_types, struct unpack_trees_options *o);
+
+static int apply_sparse_checkout(struct cache_entry *ce, struct unpack_trees_options *o)
+{
+       int was_skip_worktree = ce_skip_worktree(ce);
+
+       if (ce->ce_flags & CE_NEW_SKIP_WORKTREE)
+               ce->ce_flags |= CE_SKIP_WORKTREE;
+       else
+               ce->ce_flags &= ~CE_SKIP_WORKTREE;
+
+       /*
+        * if (!was_skip_worktree && !ce_skip_worktree()) {
+        *      This is perfectly normal. Move on;
+        * }
+        */
+
+       /*
+        * Merge strategies may set CE_UPDATE|CE_REMOVE outside checkout
+        * area as a result of ce_skip_worktree() shortcuts in
+        * verify_absent() and verify_uptodate().
+        * Make sure they don't modify worktree if they are already
+        * outside checkout area
+        */
+       if (was_skip_worktree && ce_skip_worktree(ce)) {
+               ce->ce_flags &= ~CE_UPDATE;
+
+               /*
+                * By default, when CE_REMOVE is on, CE_WT_REMOVE is also
+                * on to get that file removed from both index and worktree.
+                * If that file is already outside worktree area, don't
+                * bother remove it.
+                */
+               if (ce->ce_flags & CE_REMOVE)
+                       ce->ce_flags &= ~CE_WT_REMOVE;
+       }
+
+       if (!was_skip_worktree && ce_skip_worktree(ce)) {
+               /*
+                * If CE_UPDATE is set, verify_uptodate() must be called already
+                * also stat info may have lost after merged_entry() so calling
+                * verify_uptodate() again may fail
+                */
+               if (!(ce->ce_flags & CE_UPDATE) && verify_uptodate_sparse(ce, o))
+                       return -1;
+               ce->ce_flags |= CE_WT_REMOVE;
+       }
+       if (was_skip_worktree && !ce_skip_worktree(ce)) {
+               if (verify_absent_sparse(ce, ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o))
+                       return -1;
+               ce->ce_flags |= CE_UPDATE;
+       }
+       return 0;
+}
+
 static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_options *o)
 {
        int ret = o->fn(src, o);
@@ -126,24 +292,149 @@ static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_o
        return ret;
 }
 
-static int unpack_index_entry(struct cache_entry *ce, struct unpack_trees_options *o)
+static void mark_ce_used(struct cache_entry *ce, struct unpack_trees_options *o)
+{
+       ce->ce_flags |= CE_UNPACKED;
+
+       if (o->cache_bottom < o->src_index->cache_nr &&
+           o->src_index->cache[o->cache_bottom] == ce) {
+               int bottom = o->cache_bottom;
+               while (bottom < o->src_index->cache_nr &&
+                      o->src_index->cache[bottom]->ce_flags & CE_UNPACKED)
+                       bottom++;
+               o->cache_bottom = bottom;
+       }
+}
+
+static void mark_all_ce_unused(struct index_state *index)
+{
+       int i;
+       for (i = 0; i < index->cache_nr; i++)
+               index->cache[i]->ce_flags &= ~(CE_UNPACKED | CE_ADDED | CE_NEW_SKIP_WORKTREE);
+}
+
+static int locate_in_src_index(struct cache_entry *ce,
+                              struct unpack_trees_options *o)
+{
+       struct index_state *index = o->src_index;
+       int len = ce_namelen(ce);
+       int pos = index_name_pos(index, ce->name, len);
+       if (pos < 0)
+               pos = -1 - pos;
+       return pos;
+}
+
+/*
+ * We call unpack_index_entry() with an unmerged cache entry
+ * only in diff-index, and it wants a single callback.  Skip
+ * the other unmerged entry with the same name.
+ */
+static void mark_ce_used_same_name(struct cache_entry *ce,
+                                  struct unpack_trees_options *o)
+{
+       struct index_state *index = o->src_index;
+       int len = ce_namelen(ce);
+       int pos;
+
+       for (pos = locate_in_src_index(ce, o); pos < index->cache_nr; pos++) {
+               struct cache_entry *next = index->cache[pos];
+               if (len != ce_namelen(next) ||
+                   memcmp(ce->name, next->name, len))
+                       break;
+               mark_ce_used(next, o);
+       }
+}
+
+static struct cache_entry *next_cache_entry(struct unpack_trees_options *o)
+{
+       const struct index_state *index = o->src_index;
+       int pos = o->cache_bottom;
+
+       while (pos < index->cache_nr) {
+               struct cache_entry *ce = index->cache[pos];
+               if (!(ce->ce_flags & CE_UNPACKED))
+                       return ce;
+               pos++;
+       }
+       return NULL;
+}
+
+static void add_same_unmerged(struct cache_entry *ce,
+                             struct unpack_trees_options *o)
 {
-       struct cache_entry *src[5] = { ce, NULL, };
+       struct index_state *index = o->src_index;
+       int len = ce_namelen(ce);
+       int pos = index_name_pos(index, ce->name, len);
+
+       if (0 <= pos)
+               die("programming error in a caller of mark_ce_used_same_name");
+       for (pos = -pos - 1; pos < index->cache_nr; pos++) {
+               struct cache_entry *next = index->cache[pos];
+               if (len != ce_namelen(next) ||
+                   memcmp(ce->name, next->name, len))
+                       break;
+               add_entry(o, next, 0, 0);
+               mark_ce_used(next, o);
+       }
+}
 
-       o->pos++;
+static int unpack_index_entry(struct cache_entry *ce,
+                             struct unpack_trees_options *o)
+{
+       struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
+       int ret;
+
+       src[0] = ce;
+
+       mark_ce_used(ce, o);
        if (ce_stage(ce)) {
                if (o->skip_unmerged) {
                        add_entry(o, ce, 0, 0);
                        return 0;
                }
        }
-       return call_unpack_fn(src, o);
+       ret = call_unpack_fn(src, o);
+       if (ce_stage(ce))
+               mark_ce_used_same_name(ce, o);
+       return ret;
 }
 
-static int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
+static int find_cache_pos(struct traverse_info *, const struct name_entry *);
+
+static void restore_cache_bottom(struct traverse_info *info, int bottom)
 {
-       int i;
+       struct unpack_trees_options *o = info->data;
+
+       if (o->diff_index_cached)
+               return;
+       o->cache_bottom = bottom;
+}
+
+static int switch_cache_bottom(struct traverse_info *info)
+{
+       struct unpack_trees_options *o = info->data;
+       int ret, pos;
+
+       if (o->diff_index_cached)
+               return 0;
+       ret = o->cache_bottom;
+       pos = find_cache_pos(info->prev, &info->name);
+
+       if (pos < -1)
+               o->cache_bottom = -2 - pos;
+       else if (pos < 0)
+               o->cache_bottom = o->src_index->cache_nr;
+       return ret;
+}
+
+static int traverse_trees_recursive(int n, unsigned long dirmask,
+                                   unsigned long df_conflicts,
+                                   struct name_entry *names,
+                                   struct traverse_info *info)
+{
+       int i, ret, bottom;
        struct tree_desc t[MAX_UNPACK_TREES];
+       void *buf[MAX_UNPACK_TREES];
        struct traverse_info newinfo;
        struct name_entry *p;
 
@@ -161,9 +452,17 @@ static int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long
                const unsigned char *sha1 = NULL;
                if (dirmask & 1)
                        sha1 = names[i].sha1;
-               fill_tree_descriptor(t+i, sha1);
+               buf[i] = fill_tree_descriptor(t+i, sha1);
        }
-       return traverse_trees(n, t, &newinfo);
+
+       bottom = switch_cache_bottom(&newinfo);
+       ret = traverse_trees(n, t, &newinfo);
+       restore_cache_bottom(&newinfo, bottom);
+
+       for (i = 0; i < n; i++)
+               free(buf[i]);
+
+       return ret;
 }
 
 /*
@@ -212,6 +511,20 @@ static int compare_entry(const struct cache_entry *ce, const struct traverse_inf
        return ce_namelen(ce) > traverse_path_len(info, n);
 }
 
+static int ce_in_traverse_path(const struct cache_entry *ce,
+                              const struct traverse_info *info)
+{
+       if (!info->prev)
+               return 1;
+       if (do_compare_entry(ce, info->prev, &info->name))
+               return 0;
+       /*
+        * If ce (blob) is the same name as the path (which is a tree
+        * we will be descending into), it won't be inside it.
+        */
+       return (info->pathlen < ce_namelen(ce));
+}
+
 static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 {
        int len = traverse_path_len(info, n);
@@ -288,6 +601,122 @@ static int unpack_failed(struct unpack_trees_options *o, const char *message)
        return -1;
 }
 
+/* NEEDSWORK: give this a better name and share with tree-walk.c */
+static int name_compare(const char *a, int a_len,
+                       const char *b, int b_len)
+{
+       int len = (a_len < b_len) ? a_len : b_len;
+       int cmp = memcmp(a, b, len);
+       if (cmp)
+               return cmp;
+       return (a_len - b_len);
+}
+
+/*
+ * The tree traversal is looking at name p.  If we have a matching entry,
+ * return it.  If name p is a directory in the index, do not return
+ * anything, as we will want to match it when the traversal descends into
+ * the directory.
+ */
+static int find_cache_pos(struct traverse_info *info,
+                         const struct name_entry *p)
+{
+       int pos;
+       struct unpack_trees_options *o = info->data;
+       struct index_state *index = o->src_index;
+       int pfxlen = info->pathlen;
+       int p_len = tree_entry_len(p->path, p->sha1);
+
+       for (pos = o->cache_bottom; pos < index->cache_nr; pos++) {
+               struct cache_entry *ce = index->cache[pos];
+               const char *ce_name, *ce_slash;
+               int cmp, ce_len;
+
+               if (ce->ce_flags & CE_UNPACKED) {
+                       /*
+                        * cache_bottom entry is already unpacked, so
+                        * we can never match it; don't check it
+                        * again.
+                        */
+                       if (pos == o->cache_bottom)
+                               ++o->cache_bottom;
+                       continue;
+               }
+               if (!ce_in_traverse_path(ce, info))
+                       continue;
+               ce_name = ce->name + pfxlen;
+               ce_slash = strchr(ce_name, '/');
+               if (ce_slash)
+                       ce_len = ce_slash - ce_name;
+               else
+                       ce_len = ce_namelen(ce) - pfxlen;
+               cmp = name_compare(p->path, p_len, ce_name, ce_len);
+               /*
+                * Exact match; if we have a directory we need to
+                * delay returning it.
+                */
+               if (!cmp)
+                       return ce_slash ? -2 - pos : pos;
+               if (0 < cmp)
+                       continue; /* keep looking */
+               /*
+                * ce_name sorts after p->path; could it be that we
+                * have files under p->path directory in the index?
+                * E.g.  ce_name == "t-i", and p->path == "t"; we may
+                * have "t/a" in the index.
+                */
+               if (p_len < ce_len && !memcmp(ce_name, p->path, p_len) &&
+                   ce_name[p_len] < '/')
+                       continue; /* keep looking */
+               break;
+       }
+       return -1;
+}
+
+static struct cache_entry *find_cache_entry(struct traverse_info *info,
+                                           const struct name_entry *p)
+{
+       int pos = find_cache_pos(info, p);
+       struct unpack_trees_options *o = info->data;
+
+       if (0 <= pos)
+               return o->src_index->cache[pos];
+       else
+               return NULL;
+}
+
+static void debug_path(struct traverse_info *info)
+{
+       if (info->prev) {
+               debug_path(info->prev);
+               if (*info->prev->name.path)
+                       putchar('/');
+       }
+       printf("%s", info->name.path);
+}
+
+static void debug_name_entry(int i, struct name_entry *n)
+{
+       printf("ent#%d %06o %s\n", i,
+              n->path ? n->mode : 0,
+              n->path ? n->path : "(missing)");
+}
+
+static void debug_unpack_callback(int n,
+                                 unsigned long mask,
+                                 unsigned long dirmask,
+                                 struct name_entry *names,
+                                 struct traverse_info *info)
+{
+       int i;
+       printf("* unpack mask %lu, dirmask %lu, cnt %d ",
+              mask, dirmask, n);
+       debug_path(info);
+       putchar('\n');
+       for (i = 0; i < n; i++)
+               debug_name_entry(i, names + i);
+}
+
 static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 {
        struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
@@ -298,25 +727,38 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
        while (!p->mode)
                p++;
 
+       if (o->debug_unpack)
+               debug_unpack_callback(n, mask, dirmask, names, info);
+
        /* Are we supposed to look at the index too? */
        if (o->merge) {
-               while (o->pos < o->src_index->cache_nr) {
-                       struct cache_entry *ce = o->src_index->cache[o->pos];
-                       int cmp = compare_entry(ce, info, p);
+               while (1) {
+                       int cmp;
+                       struct cache_entry *ce;
+
+                       if (o->diff_index_cached)
+                               ce = next_cache_entry(o);
+                       else
+                               ce = find_cache_entry(info, p);
+
+                       if (!ce)
+                               break;
+                       cmp = compare_entry(ce, info, p);
                        if (cmp < 0) {
                                if (unpack_index_entry(ce, o) < 0)
                                        return unpack_failed(o, NULL);
                                continue;
                        }
                        if (!cmp) {
-                               o->pos++;
                                if (ce_stage(ce)) {
                                        /*
-                                        * If we skip unmerged index entries, we'll skip this
-                                        * entry *and* the tree entries associated with it!
+                                        * If we skip unmerged index
+                                        * entries, we'll skip this
+                                        * entry *and* the tree
+                                        * entries associated with it!
                                         */
                                        if (o->skip_unmerged) {
-                                               add_entry(o, ce, 0, 0);
+                                               add_same_unmerged(ce, o);
                                                return mask;
                                        }
                                }
@@ -329,6 +771,13 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
        if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
                return -1;
 
+       if (src[0]) {
+               if (ce_stage(src[0]))
+                       mark_ce_used_same_name(src[0], o);
+               else
+                       mark_ce_used(src[0], o);
+       }
+
        /* Now handle any directories.. */
        if (dirmask) {
                unsigned long conflicts = mask & ~dirmask;
@@ -345,11 +794,13 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
                        matches = cache_tree_matches_traversal(o->src_index->cache_tree,
                                                               names, info);
                        /*
-                        * Everything under the name matches.  Adjust o->pos to
-                        * skip the entire hierarchy.
+                        * Everything under the name matches; skip the
+                        * entire hierarchy.  diff_index_cached codepath
+                        * special cases D/F conflicts in such a way that
+                        * it does not do any look-ahead, so this is safe.
                         */
                        if (matches) {
-                               o->pos += matches;
+                               o->cache_bottom += matches;
                                return mask;
                        }
                }
@@ -363,14 +814,183 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
        return mask;
 }
 
+/* Whole directory matching */
+static int clear_ce_flags_dir(struct cache_entry **cache, int nr,
+                             char *prefix, int prefix_len,
+                             char *basename,
+                             int select_mask, int clear_mask,
+                             struct exclude_list *el)
+{
+       struct cache_entry **cache_end = cache + nr;
+       int dtype = DT_DIR;
+       int ret = excluded_from_list(prefix, prefix_len, basename, &dtype, el);
+
+       prefix[prefix_len++] = '/';
+
+       /* included, no clearing for any entries under this directory */
+       if (!ret) {
+               for (; cache != cache_end; cache++) {
+                       struct cache_entry *ce = *cache;
+                       if (strncmp(ce->name, prefix, prefix_len))
+                               break;
+               }
+               return nr - (cache_end - cache);
+       }
+
+       /* excluded, clear all selected entries under this directory. */
+       if (ret == 1) {
+               for (; cache != cache_end; cache++) {
+                       struct cache_entry *ce = *cache;
+                       if (select_mask && !(ce->ce_flags & select_mask))
+                               continue;
+                       if (strncmp(ce->name, prefix, prefix_len))
+                               break;
+                       ce->ce_flags &= ~clear_mask;
+               }
+               return nr - (cache_end - cache);
+       }
+
+       return 0;
+}
+
+/*
+ * Traverse the index, find every entry that matches according to
+ * o->el. Do "ce_flags &= ~clear_mask" on those entries. Return the
+ * number of traversed entries.
+ *
+ * If select_mask is non-zero, only entries whose ce_flags has on of
+ * those bits enabled are traversed.
+ *
+ * cache       : pointer to an index entry
+ * prefix_len  : an offset to its path
+ *
+ * The current path ("prefix") including the trailing '/' is
+ *   cache[0]->name[0..(prefix_len-1)]
+ * Top level path has prefix_len zero.
+ */
+static int clear_ce_flags_1(struct cache_entry **cache, int nr,
+                           char *prefix, int prefix_len,
+                           int select_mask, int clear_mask,
+                           struct exclude_list *el)
+{
+       struct cache_entry **cache_end = cache + nr;
+
+       /*
+        * Process all entries that have the given prefix and meet
+        * select_mask condition
+        */
+       while(cache != cache_end) {
+               struct cache_entry *ce = *cache;
+               const char *name, *slash;
+               int len, dtype;
+
+               if (select_mask && !(ce->ce_flags & select_mask)) {
+                       cache++;
+                       continue;
+               }
+
+               if (prefix_len && strncmp(ce->name, prefix, prefix_len))
+                       break;
+
+               name = ce->name + prefix_len;
+               slash = strchr(name, '/');
+
+               /* If it's a directory, try whole directory match first */
+               if (slash) {
+                       int processed;
+
+                       len = slash - name;
+                       memcpy(prefix + prefix_len, name, len);
+
+                       /*
+                        * terminate the string (no trailing slash),
+                        * clear_c_f_dir needs it
+                        */
+                       prefix[prefix_len + len] = '\0';
+                       processed = clear_ce_flags_dir(cache, cache_end - cache,
+                                                      prefix, prefix_len + len,
+                                                      prefix + prefix_len,
+                                                      select_mask, clear_mask,
+                                                      el);
+
+                       /* clear_c_f_dir eats a whole dir already? */
+                       if (processed) {
+                               cache += processed;
+                               continue;
+                       }
+
+                       prefix[prefix_len + len++] = '/';
+                       cache += clear_ce_flags_1(cache, cache_end - cache,
+                                                 prefix, prefix_len + len,
+                                                 select_mask, clear_mask, el);
+                       continue;
+               }
+
+               /* Non-directory */
+               dtype = ce_to_dtype(ce);
+               if (excluded_from_list(ce->name, ce_namelen(ce), name, &dtype, el) > 0)
+                       ce->ce_flags &= ~clear_mask;
+               cache++;
+       }
+       return nr - (cache_end - cache);
+}
+
+static int clear_ce_flags(struct cache_entry **cache, int nr,
+                           int select_mask, int clear_mask,
+                           struct exclude_list *el)
+{
+       char prefix[PATH_MAX];
+       return clear_ce_flags_1(cache, nr,
+                               prefix, 0,
+                               select_mask, clear_mask,
+                               el);
+}
+
+/*
+ * Set/Clear CE_NEW_SKIP_WORKTREE according to $GIT_DIR/info/sparse-checkout
+ */
+static void mark_new_skip_worktree(struct exclude_list *el,
+                                  struct index_state *the_index,
+                                  int select_flag, int skip_wt_flag)
+{
+       int i;
+
+       /*
+        * 1. Pretend the narrowest worktree: only unmerged entries
+        * are checked out
+        */
+       for (i = 0; i < the_index->cache_nr; i++) {
+               struct cache_entry *ce = the_index->cache[i];
+
+               if (select_flag && !(ce->ce_flags & select_flag))
+                       continue;
+
+               if (!ce_stage(ce))
+                       ce->ce_flags |= skip_wt_flag;
+               else
+                       ce->ce_flags &= ~skip_wt_flag;
+       }
+
+       /*
+        * 2. Widen worktree according to sparse-checkout file.
+        * Matched entries will have skip_wt_flag cleared (i.e. "in")
+        */
+       clear_ce_flags(the_index->cache, the_index->cache_nr,
+                      select_flag, skip_wt_flag, el);
+}
+
+static int verify_absent(struct cache_entry *, enum unpack_trees_error_types, struct unpack_trees_options *);
 /*
  * N-way merge "len" trees.  Returns 0 on success, -1 on failure to manipulate the
  * resulting index, -2 on failure to reflect the changes to the work tree.
+ *
+ * CE_ADDED, CE_UNPACKED and CE_NEW_SKIP_WORKTREE are used internally
  */
 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 {
-       int ret;
+       int i, ret;
        static struct cache_entry *dfc;
+       struct exclude_list el;
 
        if (len > MAX_UNPACK_TREES)
                die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
@@ -380,13 +1000,28 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
        state.quiet = 1;
        state.refresh_cache = 1;
 
+       memset(&el, 0, sizeof(el));
+       if (!core_apply_sparse_checkout || !o->update)
+               o->skip_sparse_checkout = 1;
+       if (!o->skip_sparse_checkout) {
+               if (add_excludes_from_file_to_list(git_path("info/sparse-checkout"), "", 0, NULL, &el, 0) < 0)
+                       o->skip_sparse_checkout = 1;
+               else
+                       o->el = &el;
+       }
+
        memset(&o->result, 0, sizeof(o->result));
        o->result.initialized = 1;
-       if (o->src_index) {
-               o->result.timestamp.sec = o->src_index->timestamp.sec;
-               o->result.timestamp.nsec = o->src_index->timestamp.nsec;
-       }
+       o->result.timestamp.sec = o->src_index->timestamp.sec;
+       o->result.timestamp.nsec = o->src_index->timestamp.nsec;
        o->merge_size = len;
+       mark_all_ce_unused(o->src_index);
+
+       /*
+        * Sparse checkout loop #1: set NEW_SKIP_WORKTREE on existing entries
+        */
+       if (!o->skip_sparse_checkout)
+               mark_new_skip_worktree(o->el, o->src_index, 0, CE_NEW_SKIP_WORKTREE);
 
        if (!dfc)
                dfc = xcalloc(1, cache_entry_size(0));
@@ -399,35 +1034,108 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
                setup_traverse_info(&info, prefix);
                info.fn = unpack_callback;
                info.data = o;
+               info.show_all_errors = o->show_all_errors;
+
+               if (o->prefix) {
+                       /*
+                        * Unpack existing index entries that sort before the
+                        * prefix the tree is spliced into.  Note that o->merge
+                        * is always true in this case.
+                        */
+                       while (1) {
+                               struct cache_entry *ce = next_cache_entry(o);
+                               if (!ce)
+                                       break;
+                               if (ce_in_traverse_path(ce, &info))
+                                       break;
+                               if (unpack_index_entry(ce, o) < 0)
+                                       goto return_failed;
+                       }
+               }
 
                if (traverse_trees(len, t, &info) < 0)
-                       return unpack_failed(o, NULL);
+                       goto return_failed;
        }
 
        /* Any left-over entries in the index? */
        if (o->merge) {
-               while (o->pos < o->src_index->cache_nr) {
-                       struct cache_entry *ce = o->src_index->cache[o->pos];
+               while (1) {
+                       struct cache_entry *ce = next_cache_entry(o);
+                       if (!ce)
+                               break;
                        if (unpack_index_entry(ce, o) < 0)
-                               return unpack_failed(o, NULL);
+                               goto return_failed;
                }
        }
+       mark_all_ce_unused(o->src_index);
+
+       if (o->trivial_merges_only && o->nontrivial_merge) {
+               ret = unpack_failed(o, "Merge requires file-level merging");
+               goto done;
+       }
+
+       if (!o->skip_sparse_checkout) {
+               int empty_worktree = 1;
+
+               /*
+                * Sparse checkout loop #2: set NEW_SKIP_WORKTREE on entries not in loop #1
+                * If the will have NEW_SKIP_WORKTREE, also set CE_SKIP_WORKTREE
+                * so apply_sparse_checkout() won't attempt to remove it from worktree
+                */
+               mark_new_skip_worktree(o->el, &o->result, CE_ADDED, CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
 
-       if (o->trivial_merges_only && o->nontrivial_merge)
-               return unpack_failed(o, "Merge requires file-level merging");
+               for (i = 0; i < o->result.cache_nr; i++) {
+                       struct cache_entry *ce = o->result.cache[i];
+
+                       /*
+                        * Entries marked with CE_ADDED in merged_entry() do not have
+                        * verify_absent() check (the check is effectively disabled
+                        * because CE_NEW_SKIP_WORKTREE is set unconditionally).
+                        *
+                        * Do the real check now because we have had
+                        * correct CE_NEW_SKIP_WORKTREE
+                        */
+                       if (ce->ce_flags & CE_ADDED &&
+                           verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o))
+                                       return -1;
+
+                       if (apply_sparse_checkout(ce, o)) {
+                               ret = -1;
+                               goto done;
+                       }
+                       if (!ce_skip_worktree(ce))
+                               empty_worktree = 0;
+
+               }
+               if (o->result.cache_nr && empty_worktree) {
+                       /* dubious---why should this fail??? */
+                       ret = unpack_failed(o, "Sparse checkout leaves no entry on working directory");
+                       goto done;
+               }
+       }
 
        o->src_index = NULL;
        ret = check_updates(o) ? (-2) : 0;
        if (o->dst_index)
                *o->dst_index = o->result;
+
+done:
+       free_excludes(&el);
        return ret;
+
+return_failed:
+       if (o->show_all_errors)
+               display_error_msgs(o);
+       mark_all_ce_unused(o->src_index);
+       ret = unpack_failed(o, NULL);
+       goto done;
 }
 
 /* Here come the merge functions */
 
 static int reject_merge(struct cache_entry *ce, struct unpack_trees_options *o)
 {
-       return error(ERRORMSG(o, would_overwrite), ce->name);
+       return add_rejected_path(o, ERROR_WOULD_OVERWRITE, ce->name);
 }
 
 static int same(struct cache_entry *a, struct cache_entry *b)
@@ -436,6 +1144,8 @@ static int same(struct cache_entry *a, struct cache_entry *b)
                return 0;
        if (!a && !b)
                return 1;
+       if ((a->ce_flags | b->ce_flags) & CE_CONFLICTED)
+               return 0;
        return a->ce_mode == b->ce_mode &&
               !hashcmp(a->sha1, b->sha1);
 }
@@ -445,16 +1155,17 @@ static int same(struct cache_entry *a, struct cache_entry *b)
  * When a CE gets turned into an unmerged entry, we
  * want it to be up-to-date
  */
-static int verify_uptodate(struct cache_entry *ce,
-               struct unpack_trees_options *o)
+static int verify_uptodate_1(struct cache_entry *ce,
+                                  struct unpack_trees_options *o,
+                                  enum unpack_trees_error_types error_type)
 {
        struct stat st;
 
-       if (o->index_only || o->reset || ce_uptodate(ce))
+       if (o->index_only || (!((ce->ce_flags & CE_VALID) || ce_skip_worktree(ce)) && (o->reset || ce_uptodate(ce))))
                return 0;
 
        if (!lstat(ce->name, &st)) {
-               unsigned changed = ie_match_stat(o->src_index, ce, &st, CE_MATCH_IGNORE_VALID);
+               unsigned changed = ie_match_stat(o->src_index, ce, &st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
                if (!changed)
                        return 0;
                /*
@@ -471,7 +1182,21 @@ static int verify_uptodate(struct cache_entry *ce,
        if (errno == ENOENT)
                return 0;
        return o->gently ? -1 :
-               error(ERRORMSG(o, not_uptodate_file), ce->name);
+               add_rejected_path(o, error_type, ce->name);
+}
+
+static int verify_uptodate(struct cache_entry *ce,
+                          struct unpack_trees_options *o)
+{
+       if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
+               return 0;
+       return verify_uptodate_1(ce, o, ERROR_NOT_UPTODATE_FILE);
+}
+
+static int verify_uptodate_sparse(struct cache_entry *ce,
+                                 struct unpack_trees_options *o)
+{
+       return verify_uptodate_1(ce, o, ERROR_SPARSE_NOT_UPTODATE_FILE);
 }
 
 static void invalidate_ce_path(struct cache_entry *ce, struct unpack_trees_options *o)
@@ -487,13 +1212,15 @@ static void invalidate_ce_path(struct cache_entry *ce, struct unpack_trees_optio
  * Currently, git does not checkout subprojects during a superproject
  * checkout, so it is not going to overwrite anything.
  */
-static int verify_clean_submodule(struct cache_entry *ce, const char *action,
+static int verify_clean_submodule(struct cache_entry *ce,
+                                     enum unpack_trees_error_types error_type,
                                      struct unpack_trees_options *o)
 {
        return 0;
 }
 
-static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
+static int verify_clean_subdirectory(struct cache_entry *ce,
+                                     enum unpack_trees_error_types error_type,
                                      struct unpack_trees_options *o)
 {
        /*
@@ -514,7 +1241,7 @@ static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
                 */
                if (!hashcmp(sha1, ce->sha1))
                        return 0;
-               return verify_clean_submodule(ce, action, o);
+               return verify_clean_submodule(ce, error_type, o);
        }
 
        /*
@@ -522,7 +1249,9 @@ static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
         * in that directory.
         */
        namelen = strlen(ce->name);
-       for (i = o->pos; i < o->src_index->cache_nr; i++) {
+       for (i = locate_in_src_index(ce, o);
+            i < o->src_index->cache_nr;
+            i++) {
                struct cache_entry *ce2 = o->src_index->cache[i];
                int len = ce_namelen(ce2);
                if (len < namelen ||
@@ -530,12 +1259,14 @@ static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
                    ce2->name[namelen] != '/')
                        break;
                /*
-                * ce2->name is an entry in the subdirectory.
+                * ce2->name is an entry in the subdirectory to be
+                * removed.
                 */
                if (!ce_stage(ce2)) {
                        if (verify_uptodate(ce2, o))
                                return -1;
                        add_entry(o, ce2, CE_REMOVE, 0);
+                       mark_ce_used(ce2, o);
                }
                cnt++;
        }
@@ -554,7 +1285,7 @@ static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
        i = read_directory(&d, pathbuf, namelen+1, NULL);
        if (i)
                return o->gently ? -1 :
-                       error(ERRORMSG(o, not_uptodate_dir), ce->name);
+                       add_rejected_path(o, ERROR_NOT_UPTODATE_DIR, ce->name);
        free(pathbuf);
        return cnt;
 }
@@ -567,98 +1298,122 @@ static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
  * See if we can find a case-insensitive match in the index that also
  * matches the stat information, and assume it's that other file!
  */
-static int icase_exists(struct unpack_trees_options *o, struct cache_entry *dst, struct stat *st)
+static int icase_exists(struct unpack_trees_options *o, const char *name, int len, struct stat *st)
 {
        struct cache_entry *src;
 
-       src = index_name_exists(o->src_index, dst->name, ce_namelen(dst), 1);
-       return src && !ie_match_stat(o->src_index, src, st, CE_MATCH_IGNORE_VALID);
+       src = index_name_exists(o->src_index, name, len, 1);
+       return src && !ie_match_stat(o->src_index, src, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
+}
+
+static int check_ok_to_remove(const char *name, int len, int dtype,
+                             struct cache_entry *ce, struct stat *st,
+                             enum unpack_trees_error_types error_type,
+                             struct unpack_trees_options *o)
+{
+       struct cache_entry *result;
+
+       /*
+        * It may be that the 'lstat()' succeeded even though
+        * target 'ce' was absent, because there is an old
+        * entry that is different only in case..
+        *
+        * Ignore that lstat() if it matches.
+        */
+       if (ignore_case && icase_exists(o, name, len, st))
+               return 0;
+
+       if (o->dir && excluded(o->dir, name, &dtype))
+               /*
+                * ce->name is explicitly excluded, so it is Ok to
+                * overwrite it.
+                */
+               return 0;
+       if (S_ISDIR(st->st_mode)) {
+               /*
+                * We are checking out path "foo" and
+                * found "foo/." in the working tree.
+                * This is tricky -- if we have modified
+                * files that are in "foo/" we would lose
+                * them.
+                */
+               if (verify_clean_subdirectory(ce, error_type, o) < 0)
+                       return -1;
+               return 0;
+       }
+
+       /*
+        * The previous round may already have decided to
+        * delete this path, which is in a subdirectory that
+        * is being replaced with a blob.
+        */
+       result = index_name_exists(&o->result, name, len, 0);
+       if (result) {
+               if (result->ce_flags & CE_REMOVE)
+                       return 0;
+       }
+
+       return o->gently ? -1 :
+               add_rejected_path(o, error_type, name);
 }
 
 /*
  * We do not want to remove or overwrite a working tree file that
  * is not tracked, unless it is ignored.
  */
-static int verify_absent(struct cache_entry *ce, const char *action,
-                        struct unpack_trees_options *o)
+static int verify_absent_1(struct cache_entry *ce,
+                                enum unpack_trees_error_types error_type,
+                                struct unpack_trees_options *o)
 {
+       int len;
        struct stat st;
 
        if (o->index_only || o->reset || !o->update)
                return 0;
 
-       if (has_symlink_or_noent_leading_path(ce->name, ce_namelen(ce)))
+       len = check_leading_path(ce->name, ce_namelen(ce));
+       if (!len)
                return 0;
+       else if (len > 0) {
+               char path[PATH_MAX + 1];
+               memcpy(path, ce->name, len);
+               path[len] = 0;
+               if (lstat(path, &st))
+                       return error("cannot stat '%s': %s", path,
+                                       strerror(errno));
+
+               return check_ok_to_remove(path, len, DT_UNKNOWN, NULL, &st,
+                               error_type, o);
+       } else if (lstat(ce->name, &st)) {
+               if (errno != ENOENT)
+                       return error("cannot stat '%s': %s", ce->name,
+                                    strerror(errno));
+               return 0;
+       } else {
+               return check_ok_to_remove(ce->name, ce_namelen(ce),
+                                         ce_to_dtype(ce), ce, &st,
+                                         error_type, o);
+       }
+}
 
-       if (!lstat(ce->name, &st)) {
-               int ret;
-               int dtype = ce_to_dtype(ce);
-               struct cache_entry *result;
-
-               /*
-                * It may be that the 'lstat()' succeeded even though
-                * target 'ce' was absent, because there is an old
-                * entry that is different only in case..
-                *
-                * Ignore that lstat() if it matches.
-                */
-               if (ignore_case && icase_exists(o, ce, &st))
-                       return 0;
-
-               if (o->dir && excluded(o->dir, ce->name, &dtype))
-                       /*
-                        * ce->name is explicitly excluded, so it is Ok to
-                        * overwrite it.
-                        */
-                       return 0;
-               if (S_ISDIR(st.st_mode)) {
-                       /*
-                        * We are checking out path "foo" and
-                        * found "foo/." in the working tree.
-                        * This is tricky -- if we have modified
-                        * files that are in "foo/" we would lose
-                        * them.
-                        */
-                       ret = verify_clean_subdirectory(ce, action, o);
-                       if (ret < 0)
-                               return ret;
-
-                       /*
-                        * If this removed entries from the index,
-                        * what that means is:
-                        *
-                        * (1) the caller unpack_callback() saw path/foo
-                        * in the index, and it has not removed it because
-                        * it thinks it is handling 'path' as blob with
-                        * D/F conflict;
-                        * (2) we will return "ok, we placed a merged entry
-                        * in the index" which would cause o->pos to be
-                        * incremented by one;
-                        * (3) however, original o->pos now has 'path/foo'
-                        * marked with "to be removed".
-                        *
-                        * We need to increment it by the number of
-                        * deleted entries here.
-                        */
-                       o->pos += ret;
-                       return 0;
-               }
+static int verify_absent(struct cache_entry *ce,
+                        enum unpack_trees_error_types error_type,
+                        struct unpack_trees_options *o)
+{
+       if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
+               return 0;
+       return verify_absent_1(ce, error_type, o);
+}
 
-               /*
-                * The previous round may already have decided to
-                * delete this path, which is in a subdirectory that
-                * is being replaced with a blob.
-                */
-               result = index_name_exists(&o->result, ce->name, ce_namelen(ce), 0);
-               if (result) {
-                       if (result->ce_flags & CE_REMOVE)
-                               return 0;
-               }
+static int verify_absent_sparse(struct cache_entry *ce,
+                        enum unpack_trees_error_types error_type,
+                        struct unpack_trees_options *o)
+{
+       enum unpack_trees_error_types orphaned_error = error_type;
+       if (orphaned_error == ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN)
+               orphaned_error = ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN;
 
-               return o->gently ? -1 :
-                       error(ERRORMSG(o, would_lose_untracked), ce->name, action);
-       }
-       return 0;
+       return verify_absent_1(ce, orphaned_error, o);
 }
 
 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
@@ -666,7 +1421,26 @@ static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 {
        int update = CE_UPDATE;
 
-       if (old) {
+       if (!old) {
+               /*
+                * New index entries. In sparse checkout, the following
+                * verify_absent() will be delayed until after
+                * traverse_trees() finishes in unpack_trees(), then:
+                *
+                *  - CE_NEW_SKIP_WORKTREE will be computed correctly
+                *  - verify_absent() be called again, this time with
+                *    correct CE_NEW_SKIP_WORKTREE
+                *
+                * verify_absent() call here does nothing in sparse
+                * checkout (i.e. o->skip_sparse_checkout == 0)
+                */
+               update |= CE_ADDED;
+               merge->ce_flags |= CE_NEW_SKIP_WORKTREE;
+
+               if (verify_absent(merge, ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o))
+                       return -1;
+               invalidate_ce_path(merge, o);
+       } else if (!(old->ce_flags & CE_CONFLICTED)) {
                /*
                 * See if we can re-use the old CE directly?
                 * That way we get the uptodate stat info.
@@ -680,13 +1454,16 @@ static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
                } else {
                        if (verify_uptodate(old, o))
                                return -1;
+                       /* Migrate old flags over */
+                       update |= old->ce_flags & (CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
                        invalidate_ce_path(old, o);
                }
-       }
-       else {
-               if (verify_absent(merge, "overwritten", o))
-                       return -1;
-               invalidate_ce_path(merge, o);
+       } else {
+               /*
+                * Previously unmerged entry left as an existence
+                * marker by read_index_unmerged();
+                */
+               invalidate_ce_path(old, o);
        }
 
        add_entry(o, merge, update, CE_STAGEMASK);
@@ -698,11 +1475,11 @@ static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 {
        /* Did it exist in the index? */
        if (!old) {
-               if (verify_absent(ce, "removed", o))
+               if (verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o))
                        return -1;
                return 0;
        }
-       if (verify_uptodate(old, o))
+       if (!(old->ce_flags & CE_CONFLICTED) && verify_uptodate(old, o))
                return -1;
        add_entry(o, ce, CE_REMOVE, 0);
        invalidate_ce_path(ce, o);
@@ -767,7 +1544,8 @@ int threeway_merge(struct cache_entry **stages, struct unpack_trees_options *o)
                remote = NULL;
        }
 
-       /* First, if there's a #16 situation, note that to prevent #13
+       /*
+        * First, if there's a #16 situation, note that to prevent #13
         * and #14.
         */
        if (!same(remote, head)) {
@@ -781,7 +1559,8 @@ int threeway_merge(struct cache_entry **stages, struct unpack_trees_options *o)
                }
        }
 
-       /* We start with cases where the index is allowed to match
+       /*
+        * We start with cases where the index is allowed to match
         * something other than the head: #14(ALT) and #2ALT, where it
         * is permitted to match the result instead.
         */
@@ -811,12 +1590,13 @@ int threeway_merge(struct cache_entry **stages, struct unpack_trees_options *o)
        if (!head && !remote && any_anc_missing)
                return 0;
 
-       /* Under the new "aggressive" rule, we resolve mostly trivial
+       /*
+        * Under the "aggressive" rule, we resolve mostly trivial
         * cases that we historically had git-merge-one-file resolve.
         */
        if (o->aggressive) {
-               int head_deleted = !head && !df_conflict_head;
-               int remote_deleted = !remote && !df_conflict_remote;
+               int head_deleted = !head;
+               int remote_deleted = !remote;
                struct cache_entry *ce = NULL;
 
                if (index)
@@ -844,7 +1624,7 @@ int threeway_merge(struct cache_entry **stages, struct unpack_trees_options *o)
                        if (index)
                                return deleted_entry(index, index, o);
                        if (ce && !head_deleted) {
-                               if (verify_absent(ce, "removed", o))
+                               if (verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o))
                                        return -1;
                        }
                        return 0;
@@ -977,7 +1757,7 @@ int bind_merge(struct cache_entry **src,
                             o->merge_size);
        if (a && old)
                return o->gently ? -1 :
-                       error(ERRORMSG(o, bind_overlap), a->name, old->name);
+                       error(ERRORMSG(o, ERROR_BIND_OVERLAP), a->name, old->name);
        if (!a)
                return keep_entry(old, o);
        else
@@ -1004,10 +1784,10 @@ int oneway_merge(struct cache_entry **src, struct unpack_trees_options *o)
 
        if (old && same(old, a)) {
                int update = 0;
-               if (o->reset && !ce_uptodate(old)) {
+               if (o->reset && !ce_uptodate(old) && !ce_skip_worktree(old)) {
                        struct stat st;
                        if (lstat(old->name, &st) ||
-                           ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID))
+                           ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE))
                                update |= CE_UPDATE;
                }
                add_entry(o, old, update, 0);