X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=read-tree.c;h=fbd0da0ebdc5c523b7f35399a39a3b8efd373112;hb=8544a6f1b8e7340924c406d717ac37becd2f6046;hp=6862d1012681cd6812ab9bfe1a866446f92a7c91;hpb=f768846e34997fb847c9b875615867d4716d632f;p=git.git

diff --git a/read-tree.c b/read-tree.c
index 6862d101..fbd0da0e 100644
--- a/read-tree.c
+++ b/read-tree.c
@@ -5,101 +5,335 @@
  */
 #include "cache.h"
 
-static int read_one_entry(unsigned char *sha1, const char *base, int baselen, const char *pathname, unsigned mode)
-{
-	int len = strlen(pathname);
-	unsigned int size = cache_entry_size(baselen + len);
-	struct cache_entry *ce = malloc(size);
-
-	memset(ce, 0, size);
-
-	ce->st_mode = mode;
-	ce->namelen = baselen + len;
-	memcpy(ce->name, base, baselen);
-	memcpy(ce->name + baselen, pathname, len+1);
-	memcpy(ce->sha1, sha1, 20);
-	return add_cache_entry(ce);
-}
+static int stage = 0;
+static int update = 0;
 
-static int read_tree(unsigned char *sha1, const char *base, int baselen)
+static int unpack_tree(unsigned char *sha1)
 {
 	void *buffer;
 	unsigned long size;
-	char type[20];
+	int ret;
 
-	buffer = read_sha1_file(sha1, type, &size);
+	buffer = read_object_with_reference(sha1, "tree", &size, NULL);
 	if (!buffer)
 		return -1;
-	if (strcmp(type, "tree"))
-		return -1;
-	while (size) {
-		int len = strlen(buffer)+1;
-		unsigned char *sha1 = buffer + len;
-		char *path = strchr(buffer, ' ')+1;
-		unsigned int mode;
+	ret = read_tree(buffer, size, stage);
+	free(buffer);
+	return ret;
+}
+
+static int path_matches(struct cache_entry *a, struct cache_entry *b)
+{
+	int len = ce_namelen(a);
+	return ce_namelen(b) == len &&
+		!memcmp(a->name, b->name, len);
+}
+
+static int same(struct cache_entry *a, struct cache_entry *b)
+{
+	return a->ce_mode == b->ce_mode && 
+		!memcmp(a->sha1, b->sha1, 20);
+}
+
+
+/*
+ * This removes all trivial merges that don't change the tree
+ * and collapses them to state 0.
+ */
+static struct cache_entry *merge_entries(struct cache_entry *a,
+					 struct cache_entry *b,
+					 struct cache_entry *c)
+{
+	/*
+	 * Ok, all three entries describe the same
+	 * filename, but maybe the contents or file
+	 * mode have changed?
+	 *
+	 * The trivial cases end up being the ones where two
+	 * out of three files are the same:
+	 *  - both destinations the same, trivially take either
+	 *  - one of the destination versions hasn't changed,
+	 *    take the other.
+	 *
+	 * The "all entries exactly the same" case falls out as
+	 * a special case of any of the "two same" cases.
+	 *
+	 * Here "a" is "original", and "b" and "c" are the two
+	 * trees we are merging.
+	 */
+	if (a && b && c) {
+		if (same(b,c))
+			return c;
+		if (same(a,b))
+			return c;
+		if (same(a,c))
+			return b;
+	}
+	return NULL;
+}
+
+/*
+ * When a CE gets turned into an unmerged entry, we
+ * want it to be up-to-date
+ */
+static void verify_uptodate(struct cache_entry *ce)
+{
+	struct stat st;
+
+	if (!lstat(ce->name, &st)) {
+		unsigned changed = ce_match_stat(ce, &st);
+		if (!changed)
+			return;
+		errno = 0;
+	}
+	if (errno == ENOENT)
+		return;
+	die("Entry '%s' not uptodate. Cannot merge.", ce->name);
+}
+
+/*
+ * If the old tree contained a CE that isn't even in the
+ * result, that's always a problem, regardless of whether
+ * it's up-to-date or not (ie it can be a file that we
+ * have updated but not committed yet).
+ */
+static void reject_merge(struct cache_entry *ce)
+{
+	die("Entry '%s' would be overwritten by merge. Cannot merge.", ce->name);
+}
+
+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 int threeway_merge(struct cache_entry *stages[4], struct cache_entry **dst)
+{
+	struct cache_entry *old = stages[0];
+	struct cache_entry *a = stages[1], *b = stages[2], *c = stages[3];
+	struct cache_entry *merge;
+	int count;
 
-		if (size < len + 20 || sscanf(buffer, "%o", &mode) != 1)
+	/*
+	 * 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;
+}
 
-		buffer = sha1 + 20;
-		size -= len + 20;
-
-		if (S_ISDIR(mode)) {
-			int retval;
-			int pathlen = strlen(path);
-			char *newbase = malloc(baselen + 1 + pathlen);
-			memcpy(newbase, base, baselen);
-			memcpy(newbase + baselen, path, pathlen);
-			newbase[baselen + pathlen] = '/';
-			retval = read_tree(sha1, newbase, baselen + pathlen + 1);
-			free(newbase);
-			if (retval)
-				return -1;
-			continue;
+/*
+ * 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];
+
+	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 (read_one_entry(sha1, base, baselen, path, mode) < 0)
+		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;
 	}
-	return 0;
+	else if (newtree)
+		return merged_entry(newtree, NULL, dst);
+	else
+		return 0;
+}
+
+/*
+ * 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;
+	}
+	return merged_entry(a, NULL, dst);
+}
+
+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)
+{
+	struct cache_entry **dst = src;
+
+	while (nr) {
+		int entries;
+		struct cache_entry *name, *ce, *stages[4] = { NULL, };
+
+		name = ce = *src;
+		for (;;) {
+			int stage = ce_stage(ce);
+			stages[stage] = ce;
+			ce = *++src;
+			active_nr--;
+			if (!--nr)
+				break;
+			if (!path_matches(ce, name))
+				break;
+		}
+
+		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 [-u] <sha1> [<sha2> [<sha3>]])";
+
+static struct cache_file cache_file;
+
 int main(int argc, char **argv)
 {
-	int i, newfd;
+	int i, newfd, merge;
 	unsigned char sha1[20];
 
-	newfd = open(".dircache/index.lock", O_RDWR | O_CREAT | O_EXCL, 0600);
+	newfd = hold_index_file_for_update(&cache_file, get_index_file());
 	if (newfd < 0)
-		usage("unable to create new cachefile");
+		die("unable to create new cachefile");
 
+	merge = 0;
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
 
-		/* "-m" stands for "merge" current directory cache */
+		/* "-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")) {
-			if (active_cache) {
-				fprintf(stderr, "read-tree: cannot merge old cache on top of new\n");
-				goto out;
-			}
-			if (read_cache() < 0) {
-				fprintf(stderr, "read-tree: corrupt directory cache\n");
-				goto out;
+			int i;
+			if (stage)
+				die("-m needs to come first");
+			read_cache();
+			for (i = 0; i < active_nr; i++) {
+				if (ce_stage(active_cache[i]))
+					die("you need to resolve your current index first");
 			}
+			stage = 1;
+			merge = 1;
 			continue;
 		}
-		if (get_sha1_hex(arg, sha1) < 0) {
-			fprintf(stderr, "read-tree [-m] <sha1>\n");
-			goto out;
-		}
-		if (read_tree(sha1, "", 0) < 0) {
-			fprintf(stderr, "failed to unpack tree object %s\n", arg);
-			goto out;
-		}
+		if (get_sha1(arg, sha1) < 0)
+			usage(read_tree_usage);
+		if (stage > 3)
+			usage(read_tree_usage);
+		if (unpack_tree(sha1) < 0)
+			die("failed to unpack tree object %s", arg);
+		stage++;
 	}
-	if (!write_cache(newfd, active_cache, active_nr) && !rename(".dircache/index.lock", ".dircache/index"))
-		return 0;
-
-out:
-	unlink(".dircache/index.lock");
-	exit(1);
+	if (update && !merge)
+		usage(read_tree_usage);
+	if (merge) {
+		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) ||
+	    commit_index_file(&cache_file))
+		die("unable to write new index file");
+	return 0;
 }