apply: refactor "previous patch" logic

The code to grab the result of application of a previous patch in the
input was mixed with error message generation for a case where a later
patch tries to modify contents of a path that has been removed.

The same code is duplicated elsewhere in the code.  Introduce a helper
to clarify what is going on.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/apply.c b/builtin/apply.c
index 4d2546f5e1ce6a702b5dc27f34c97e78770c4f64..56424334047fdc55fcc65ba0ecc4404c24cd15cc 100644 (file)
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3046,22 +3046,50 @@ static int checkout_target(struct cache_entry *ce, struct stat *st)
        return 0;
 }
 
+static struct patch *previous_patch(struct patch *patch, int *gone)
+{
+       struct patch *previous;
+
+       *gone = 0;
+       if (patch->is_copy || patch->is_rename)
+               return NULL; /* "git" patches do not depend on the order */
+
+       previous = in_fn_table(patch->old_name);
+       if (!previous)
+               return NULL;
+
+       if (to_be_deleted(previous))
+               return NULL; /* the deletion hasn't happened yet */
+
+       if (was_deleted(previous))
+               *gone = 1;
+
+       return previous;
+}
+
+/*
+ * We are about to apply "patch"; populate the "image" with the
+ * current version we have, from the working tree or from the index,
+ * depending on the situation e.g. --cached/--index.  If we are
+ * applying a non-git patch that incrementally updates the tree,
+ * we read from the result of a previous diff.
+ */
 static int load_preimage(struct image *image,
                         struct patch *patch, struct stat *st, struct cache_entry *ce)
 {
        struct strbuf buf = STRBUF_INIT;
        size_t len;
        char *img;
-       struct patch *tpatch;
+       struct patch *previous;
+       int status;
 
-       if (!(patch->is_copy || patch->is_rename) &&
-           (tpatch = in_fn_table(patch->old_name)) != NULL && !to_be_deleted(tpatch)) {
-               if (was_deleted(tpatch)) {
-                       return error(_("patch %s has been renamed/deleted"),
-                               patch->old_name);
-               }
+       previous = previous_patch(patch, &status);
+       if (status)
+               return error(_("path %s has been renamed/deleted"),
+                            patch->old_name);
+       if (previous) {
                /* We have a patched copy in memory; use that. */
-               strbuf_add(&buf, tpatch->result, tpatch->resultsize);
+               strbuf_add(&buf, previous->result, previous->resultsize);
        } else if (cached) {
                if (read_file_or_gitlink(ce, &buf))
                        return error(_("read of %s failed"), patch->old_name);
@@ -3143,39 +3171,41 @@ static int verify_index_match(struct cache_entry *ce, struct stat *st)
        return ce_match_stat(ce, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
 }
 
+/*
+ * If "patch" that we are looking at modifies or deletes what we have,
+ * we would want it not to lose any local modification we have, either
+ * in the working tree or in the index.
+ *
+ * This also decides if a non-git patch is a creation patch or a
+ * modification to an existing empty file.  We do not check the state
+ * of the current tree for a creation patch in this function; the caller
+ * check_patch() separately makes sure (and errors out otherwise) that
+ * the path the patch creates does not exist in the current tree.
+ */
 static int check_preimage(struct patch *patch, struct cache_entry **ce, struct stat *st)
 {
        const char *old_name = patch->old_name;
-       struct patch *tpatch = NULL;
-       int stat_ret = 0;
+       struct patch *previous = NULL;
+       int stat_ret = 0, status;
        unsigned st_mode = 0;
 
-       /*
-        * Make sure that we do not have local modifications from the
-        * index when we are looking at the index.  Also make sure
-        * we have the preimage file to be patched in the work tree,
-        * unless --cached, which tells git to apply only in the index.
-        */
        if (!old_name)
                return 0;
 
        assert(patch->is_new <= 0);
+       previous = previous_patch(patch, &status);
 
-       if (!(patch->is_copy || patch->is_rename) &&
-           (tpatch = in_fn_table(old_name)) != NULL && !to_be_deleted(tpatch)) {
-               if (was_deleted(tpatch))
-                       return error(_("%s: has been deleted/renamed"), old_name);
-               st_mode = tpatch->new_mode;
+       if (status)
+               return error(_("path %s has been renamed/deleted"), old_name);
+       if (previous) {
+               st_mode = previous->new_mode;
        } else if (!cached) {
                stat_ret = lstat(old_name, st);
                if (stat_ret && errno != ENOENT)
                        return error(_("%s: %s"), old_name, strerror(errno));
        }
 
-       if (to_be_deleted(tpatch))
-               tpatch = NULL;
-
-       if (check_index && !tpatch) {
+       if (check_index && !previous) {
                int pos = cache_name_pos(old_name, strlen(old_name));
                if (pos < 0) {
                        if (patch->is_new < 0)
@@ -3197,7 +3227,7 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
                return error(_("%s: %s"), old_name, strerror(errno));
        }
 
-       if (!cached && !tpatch)
+       if (!cached && !previous)
                st_mode = ce_mode_from_stat(*ce, st->st_mode);
 
        if (patch->is_new < 0)