#include "cache.h"
static int stage = 0;
+static int update = 0;
static int unpack_tree(unsigned char *sha1)
{
return ret;
}
-static char *lockfile_name;
-
-static void remove_lock_file(void)
-{
- if (lockfile_name)
- unlink(lockfile_name);
-}
-
static int path_matches(struct cache_entry *a, struct cache_entry *b)
{
int len = ce_namelen(a);
/*
* This removes all trivial merges that don't change the tree
* and collapses them to state 0.
- *
- * _Any_ other merge is left to user policy. That includes "both
- * created the same file", and "both removed the same file" - which are
- * trivial, but the user might still want to _note_ it.
*/
static struct cache_entry *merge_entries(struct cache_entry *a,
struct cache_entry *b,
struct cache_entry *c)
{
- int len = ce_namelen(a);
-
- /*
- * Are they all the same filename? We won't do
- * any name merging
- */
- if (ce_namelen(b) != len ||
- ce_namelen(c) != len ||
- memcmp(a->name, b->name, len) ||
- memcmp(a->name, c->name, len))
- return NULL;
-
/*
* Ok, all three entries describe the same
* filename, but maybe the contents or file
* Here "a" is "original", and "b" and "c" are the two
* trees we are merging.
*/
- if (same(b,c))
- return c;
- if (same(a,b))
- return c;
- if (same(a,c))
- return b;
+ if (a && b && c) {
+ if (same(b,c))
+ return c;
+ if (same(a,b))
+ return c;
+ if (same(a,c))
+ return b;
+ }
return NULL;
}
die("Entry '%s' would be overwritten by merge. Cannot merge.", ce->name);
}
-#define CHECK_OLD(ce) if (old && same(old, ce)) { verify_uptodate(old); old = NULL; }
+static int merged_entry(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst)
+{
+ merge->ce_flags |= htons(CE_UPDATE);
+ if (old) {
+ /*
+ * See if we can re-use the old CE directly?
+ * That way we get the uptodate stat info.
+ *
+ * This also removes the UPDATE flag on
+ * a match.
+ */
+ if (same(old, merge)) {
+ *merge = *old;
+ } else {
+ verify_uptodate(old);
+ }
+ }
+ merge->ce_flags &= ~htons(CE_STAGEMASK);
+ *dst++ = merge;
+ return 1;
+}
-static void trivially_merge_cache(struct cache_entry **src, int nr)
+static int threeway_merge(struct cache_entry *stages[4], struct cache_entry **dst)
{
- struct cache_entry **dst = src;
- struct cache_entry *old = NULL;
+ struct cache_entry *old = stages[0];
+ struct cache_entry *a = stages[1], *b = stages[2], *c = stages[3];
+ struct cache_entry *merge;
+ int count;
- while (nr) {
- struct cache_entry *ce, *result;
+ /*
+ * If we have an entry in the index cache ("old"), then we want
+ * to make sure that it matches any entries in stage 2 ("first
+ * branch", aka "b").
+ */
+ if (old) {
+ if (!b || !same(old, b))
+ return -1;
+ }
+ merge = merge_entries(a, b, c);
+ if (merge)
+ return merged_entry(merge, old, dst);
+ if (old)
+ verify_uptodate(old);
+ count = 0;
+ if (a) { *dst++ = a; count++; }
+ if (b) { *dst++ = b; count++; }
+ if (c) { *dst++ = c; count++; }
+ return count;
+}
- ce = src[0];
+/*
+ * Two-way merge.
+ *
+ * The rule is to "carry forward" what is in the index without losing
+ * information across a "fast forward", favoring a successful merge
+ * over a merge failure when it makes sense. For details of the
+ * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
+ *
+ */
+static int twoway_merge(struct cache_entry **src, struct cache_entry **dst)
+{
+ struct cache_entry *current = src[0];
+ struct cache_entry *oldtree = src[1], *newtree = src[2];
- /* We throw away original cache entries except for the stat information */
- if (!ce_stage(ce)) {
- if (old)
- reject_merge(old);
- old = ce;
- src++;
- nr--;
- active_nr--;
- continue;
+ if (src[3])
+ return -1;
+
+ if (current) {
+ if ((!oldtree && !newtree) || /* 4 and 5 */
+ (!oldtree && newtree &&
+ same(current, newtree)) || /* 6 and 7 */
+ (oldtree && newtree &&
+ same(oldtree, newtree)) || /* 14 and 15 */
+ (oldtree && newtree &&
+ !same(oldtree, newtree) && /* 18 and 19*/
+ same(current, newtree))) {
+ *dst++ = current;
+ return 1;
}
- if (old && !path_matches(old, ce))
- reject_merge(old);
- if (nr > 2 && (result = merge_entries(ce, src[1], src[2])) != NULL) {
- /*
- * See if we can re-use the old CE directly?
- * That way we get the uptodate stat info.
- */
- if (old && same(old, result)) {
- *result = *old;
- old = NULL;
- }
- CHECK_OLD(ce);
- CHECK_OLD(src[1]);
- CHECK_OLD(src[2]);
- ce = result;
- ce->ce_flags &= ~htons(CE_STAGEMASK);
- src += 2;
- nr -= 2;
- active_nr -= 2;
+ else if (oldtree && !newtree && same(current, oldtree)) {
+ /* 10 or 11 */
+ verify_uptodate(current);
+ return 0;
+ }
+ else if (oldtree && newtree &&
+ same(current, oldtree) && !same(current, newtree)) {
+ /* 20 or 21 */
+ verify_uptodate(current);
+ return merged_entry(newtree, NULL, dst);
}
+ else
+ /* all other failures */
+ return -1;
+ }
+ else if (newtree)
+ return merged_entry(newtree, NULL, dst);
+ else
+ return 0;
+}
- /*
- * If we had an old entry that we now effectively
- * overwrite, make sure it wasn't dirty.
- */
- CHECK_OLD(ce);
- *dst++ = ce;
- src++;
- nr--;
+/*
+ * One-way merge.
+ *
+ * The rule is:
+ * - take the stat information from stage0, take the data from stage1
+ */
+static int oneway_merge(struct cache_entry **src, struct cache_entry **dst)
+{
+ struct cache_entry *old = src[0];
+ struct cache_entry *a = src[1];
+
+ if (src[2] || src[3])
+ return -1;
+
+ if (!a)
+ return 0;
+ if (old && same(old, a)) {
+ *dst++ = old;
+ return 1;
}
- if (old)
- reject_merge(old);
+ return merged_entry(a, NULL, dst);
}
-static void merge_stat_info(struct cache_entry **src, int nr)
+static void check_updates(struct cache_entry **src, int nr)
+{
+ static struct checkout state = {
+ .base_dir = "",
+ .force = 1,
+ .quiet = 1,
+ .refresh_cache = 1,
+ };
+ unsigned short mask = htons(CE_UPDATE);
+ while (nr--) {
+ struct cache_entry *ce = *src++;
+ if (ce->ce_flags & mask) {
+ ce->ce_flags &= ~mask;
+ if (update)
+ checkout_entry(ce, &state);
+ }
+ }
+}
+
+typedef int (*merge_fn_t)(struct cache_entry **, struct cache_entry **);
+
+static void merge_cache(struct cache_entry **src, int nr, merge_fn_t fn)
{
- static struct cache_entry null_entry;
struct cache_entry **dst = src;
- struct cache_entry *old = &null_entry;
while (nr) {
- struct cache_entry *ce;
+ int entries;
+ struct cache_entry *name, *ce, *stages[4] = { NULL, };
- ce = src[0];
-
- /* We throw away original cache entries except for the stat information */
- if (!ce_stage(ce)) {
- old = ce;
- src++;
- nr--;
+ name = ce = *src;
+ for (;;) {
+ int stage = ce_stage(ce);
+ stages[stage] = ce;
+ ce = *++src;
active_nr--;
- continue;
+ if (!--nr)
+ break;
+ if (!path_matches(ce, name))
+ break;
}
- if (path_matches(ce, old) && same(ce, old))
- *ce = *old;
- ce->ce_flags &= ~htons(CE_STAGEMASK);
- *dst++ = ce;
- src++;
- nr--;
+
+ entries = fn(stages, dst);
+ if (entries < 0)
+ reject_merge(name);
+ dst += entries;
+ active_nr += entries;
}
+ check_updates(active_cache, active_nr);
}
-static char *read_tree_usage = "git-read-tree (<sha> | -m <sha1> [<sha2> <sha3>])";
+static char *read_tree_usage = "git-read-tree (<sha> | -m [-u] <sha1> [<sha2> [<sha3>]])";
+
+static struct cache_file cache_file;
int main(int argc, char **argv)
{
int i, newfd, merge;
unsigned char sha1[20];
- static char lockfile[MAXPATHLEN+1];
- const char *indexfile = get_index_file();
- snprintf(lockfile, sizeof(lockfile), "%s.lock", indexfile);
-
- newfd = open(lockfile, O_RDWR | O_CREAT | O_EXCL, 0600);
+ newfd = hold_index_file_for_update(&cache_file, get_index_file());
if (newfd < 0)
die("unable to create new cachefile");
- atexit(remove_lock_file);
- lockfile_name = lockfile;
merge = 0;
for (i = 1; i < argc; i++) {
const char *arg = argv[i];
+ /* "-u" means "update", meaning that a merge will update the working directory */
+ if (!strcmp(arg, "-u")) {
+ update = 1;
+ continue;
+ }
+
/* "-m" stands for "merge", meaning we start in stage 1 */
if (!strcmp(arg, "-m")) {
int i;
die("failed to unpack tree object %s", arg);
stage++;
}
+ if (update && !merge)
+ usage(read_tree_usage);
if (merge) {
- switch (stage) {
- case 4: /* Three-way merge */
- trivially_merge_cache(active_cache, active_nr);
- break;
- case 2: /* Just read a tree, merge with old cache contents */
- merge_stat_info(active_cache, active_nr);
- break;
- default:
+ static const merge_fn_t merge_function[] = {
+ [1] = oneway_merge,
+ [2] = twoway_merge,
+ [3] = threeway_merge,
+ };
+ if (stage < 2 || stage > 4)
die("just how do you expect me to merge %d trees?", stage-1);
- }
+ merge_cache(active_cache, active_nr, merge_function[stage-1]);
}
- if (write_cache(newfd, active_cache, active_nr) || rename(lockfile, indexfile))
+ if (write_cache(newfd, active_cache, active_nr) ||
+ commit_index_file(&cache_file))
die("unable to write new index file");
- lockfile_name = NULL;
return 0;
}