X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=read-tree.c;h=65f2d9a5dc5dd6cf6aaa24ca90d96c5c7ab6992d;hb=ec3f5a46eae8dd36995ff4709360417b55bc2d7d;hp=9aec97fa73d4e6bd2354988536af8826dbb9ed04;hpb=2de381f919829aec1e35d6c7cc33519295dcd053;p=git.git

diff --git a/read-tree.c b/read-tree.c
index 9aec97fa..65f2d9a5 100644
--- a/read-tree.c
+++ b/read-tree.c
@@ -5,102 +5,599 @@
  */
 #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);
+static int stage = 0;
+static int update = 0;
 
-	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, 1);
-}
-
-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"))
+	ret = read_tree(buffer, size, stage, NULL);
+	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_internal(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst, int allow_dirty)
+{
+	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 if (!allow_dirty) {
+			verify_uptodate(old);
+		}
+	}
+	merge->ce_flags &= ~htons(CE_STAGEMASK);
+	*dst++ = merge;
+	return 1;
+}
+
+static int merged_entry_allow_dirty(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst)
+{
+	return merged_entry_internal(merge, old, dst, 1);
+}
+
+static int merged_entry(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst)
+{
+	return merged_entry_internal(merge, old, dst, 0);
+}
+
+static int deleted_entry(struct cache_entry *ce, struct cache_entry *old, struct cache_entry **dst)
+{
+	if (old)
+		verify_uptodate(old);
+	ce->ce_mode = 0;
+	*dst++ = ce;
+	return 1;
+}
+
+static int causes_df_conflict(struct cache_entry *ce, int stage,
+			      struct cache_entry **dst_,
+			      struct cache_entry **next_,
+			      int tail)
+{
+	/* This is called during the merge operation and walking
+	 * the active_cache[] array is messy, because it is in the
+	 * middle of overlapping copy operation.  The invariants
+	 * are:
+	 * (1) active_cache points at the first (zeroth) entry.
+	 * (2) up to dst pointer are resolved entries.
+	 * (3) from the next pointer (head-inclusive) to the tail
+	 *     of the active_cache array have the remaining paths
+	 *     to be processed.  There can be a gap between dst
+	 *     and next.  Note that next is called "src" in the
+	 *     merge_cache() function, and tail is the original
+	 *     end of active_cache array when merge_cache() started.
+	 * (4) the path corresponding to *ce is not found in (2)
+	 *     or (3).  It is in the gap.
+	 *
+	 *  active_cache -----......+++++++++++++.
+	 *                    ^dst  ^next        ^tail
+	 */
+	int i, next, dst;
+	const char *path = ce->name;
+	int namelen = ce_namelen(ce);
+
+	next = next_ - active_cache;
+	dst = dst_ - active_cache;
+
+	for (i = 0; i < tail; i++) {
+		int entlen, len;
+		const char *one, *two;
+		if (dst <= i && i < next)
+			continue;
+		ce = active_cache[i];
+		if (ce_stage(ce) != stage)
+			continue;
+		/* If ce->name is a prefix of path, then path is a file
+		 * that hangs underneath ce->name, which is bad.
+		 * If path is a prefix of ce->name, then it is the
+		 * other way around which also is bad.
+		 */
+		entlen = ce_namelen(ce);
+		if (namelen == entlen)
+			continue;
+		if (namelen < entlen) {
+			len = namelen;
+			one = path;
+			two = ce->name;
+		} else {
+			len = entlen;
+			one = ce->name;
+			two = path;
+		}
+		if (memcmp(one, two, len))
+			continue;
+		if (two[len] == '/')
+			return 1;
+	}
+	return 0;
+}
+
+static int threeway_merge(struct cache_entry *stages[4],
+			  struct cache_entry **dst,
+			  struct cache_entry **next, int tail)
+{
+	struct cache_entry *old = stages[0];
+	struct cache_entry *a = stages[1], *b = stages[2], *c = stages[3];
+	struct cache_entry *merge;
+	int count;
+
+	/* #5ALT */
+	if (!a && b && c && same(b, c)) {
+		if (old && !same(b, old))
+			return -1;
+		return merged_entry_allow_dirty(b, old, dst);
+	}
+	/* #2ALT and #3ALT */
+	if (!a && (!!b != !!c)) {
+		/*
+		 * The reason we need to worry about directory/file
+		 * conflicts only in #2ALT and #3ALT case is this:
+		 *
+		 * (1) For all other cases that read-tree internally
+		 *     resolves a path, we always have such a path in
+		 *     *both* stage2 and stage3 when we begin.
+		 *     Traditionally, the behaviour has been even
+		 *     stricter and we did not resolve a path without
+		 *     initially being in all of stage1, 2, and 3.
+		 *
+		 * (2) When read-tree finishes, all resolved paths (i.e.
+		 *     the paths that are in stage0) must have come from
+		 *     either stage2 or stage3.  It is not possible to
+		 *     have a stage0 path as a result of a merge if
+		 *     neither stage2 nor stage3 had that path.
+		 *
+		 * (3) It is guaranteed that just after reading the
+		 *     stages, each stage cannot have directory/file
+		 *     conflicts on its own, because they are populated
+		 *     by reading hierarchy of a tree.  Combined with
+		 *     (1) and (2) above, this means that no matter what
+		 *     combination of paths we take from stage2 and
+		 *     stage3 as a result of a merge, they cannot cause
+		 *     a directory/file conflict situation (otherwise
+		 *     the "guilty" path would have already had such a
+		 *     conflict in the original stage, either stage2
+		 *     or stage3).  Although its stage2 is synthesized
+		 *     by overlaying the current index on top of "our
+		 *     head" tree, --emu23 case also has this guarantee,
+		 *     by calling add_cache_entry() to create such stage2
+		 *     entries.
+		 *
+		 * (4) Only #2ALT and #3ALT lack the guarantee (1).
+		 *     They resolve paths that exist only in stage2
+		 *     or stage3.  The stage2 tree may have a file DF
+		 *     while stage3 tree may have a file DF/DF.  If
+		 *     #2ALT and #3ALT rules happen to apply to both
+		 *     of them, we would end up having DF (coming from
+		 *     stage2) and DF/DF (from stage3) in the result.
+		 *     When we attempt to resolve a path that exists
+		 *     only in stage2, we need to make sure there is
+		 *     no path that would conflict with it in stage3
+		 *     and vice versa.
+		 */
+		if (c) { /* #2ALT */
+			if (!causes_df_conflict(c, 2, dst, next, tail) &&
+			    (!old || same(c, old)))
+				return merged_entry_allow_dirty(c, old, dst);
+		}
+		else { /* #3ALT */
+			if (!causes_df_conflict(b, 3, dst, next, tail) &&
+			    (!old || same(b, old)))
+				return merged_entry_allow_dirty(b, old, dst);
+		}
+		/* otherwise we will apply the original rule */
+	}
+	/* #14ALT */
+	if (a && b && c && same(a, b) && !same(a, c)) {
+		if (old && same(old, c))
+			return merged_entry_allow_dirty(c, old, dst);
+		/* otherwise the regular rule applies */
+	}
+	/*
+	 * 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;
+}
+
+/*
+ * 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 **next, int tail)
+{
+	struct cache_entry *current = src[0];
+	struct cache_entry *oldtree = src[1], *newtree = src[2];
+
+	if (src[3])
 		return -1;
-	while (size) {
-		int len = strlen(buffer)+1;
-		unsigned char *sha1 = buffer + len;
-		char *path = strchr(buffer, ' ')+1;
-		unsigned int mode;
 
-		if (size < len + 20 || sscanf(buffer, "%o", &mode) != 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;
+		}
+		else if (oldtree && !newtree && same(current, oldtree)) {
+			/* 10 or 11 */
+			return deleted_entry(oldtree, current, dst);
+		}
+		else if (oldtree && newtree &&
+			 same(current, oldtree) && !same(current, newtree)) {
+			/* 20 or 21 */
+			return merged_entry(newtree, current, dst);
+		}
+		else
+			/* all other failures */
 			return -1;
+	}
+	else if (newtree)
+		return merged_entry(newtree, current, dst);
+	else
+		return deleted_entry(oldtree, current, dst);
+}
+
+/*
+ * Two-way merge emulated with three-way merge.
+ *
+ * This treats "read-tree -m H M" by transforming it internally
+ * into "read-tree -m H I+H M", where I+H is a tree that would
+ * contain the contents of the current index file, overlayed on
+ * top of H.  Unlike the traditional two-way merge, this leaves
+ * the stages in the resulting index file and lets the user resolve
+ * the merge conflicts using standard tools for three-way merge.
+ *
+ * This function is just to set-up such an arrangement, and the
+ * actual merge uses threeway_merge() function.
+ */
+static void setup_emu23(void)
+{
+	/* stage0 contains I, stage1 H, stage2 M.
+	 * move stage2 to stage3, and create stage2 entries
+	 * by scanning stage0 and stage1 entries.
+	 */
+	int i, namelen, size;
+	struct cache_entry *ce, *stage2;
 
-		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;
+	for (i = 0; i < active_nr; i++) {
+		ce = active_cache[i];
+		if (ce_stage(ce) != 2)
+			continue;
+		/* hoist them up to stage 3 */
+		namelen = ce_namelen(ce);
+		ce->ce_flags = create_ce_flags(namelen, 3);
+	}
+
+	for (i = 0; i < active_nr; i++) {
+		ce = active_cache[i];
+		if (ce_stage(ce) > 1)
+			continue;
+		namelen = ce_namelen(ce);
+		size = cache_entry_size(namelen);
+		stage2 = xmalloc(size);
+		memcpy(stage2, ce, size);
+		stage2->ce_flags = create_ce_flags(namelen, 2);
+		if (add_cache_entry(stage2, ADD_CACHE_OK_TO_ADD) < 0)
+			die("cannot merge index and our head tree");
+
+		/* We are done with this name, so skip to next name */
+		while (i < active_nr &&
+		       ce_namelen(active_cache[i]) == namelen &&
+		       !memcmp(active_cache[i]->name, ce->name, namelen))
+			i++;
+		i--; /* compensate for the loop control */
+	}
+}
+
+/*
+ * 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 **next, int tail)
+{
+	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_mode) {
+			if (update)
+				unlink(ce->name);
 			continue;
 		}
-		if (read_one_entry(sha1, base, baselen, path, mode) < 0)
-			return -1;
+		if (ce->ce_flags & mask) {
+			ce->ce_flags &= ~mask;
+			if (update)
+				checkout_entry(ce, &state);
+		}
 	}
-	return 0;
 }
 
-static int remove_lock = 0;
+typedef int (*merge_fn_t)(struct cache_entry **, struct cache_entry **, struct cache_entry **, int);
 
-static void remove_lock_file(void)
+static void merge_cache(struct cache_entry **src, int nr, merge_fn_t fn)
 {
-	if (remove_lock)
-		unlink(".git/index.lock");
+	struct cache_entry **dst = src;
+	int tail = nr;
+
+	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, src, tail);
+		if (entries < 0)
+			reject_merge(name);
+		dst += entries;
+		active_nr += entries;
+	}
+	check_updates(active_cache, active_nr);
 }
 
+static int read_cache_unmerged(void)
+{
+	int i, deleted;
+	struct cache_entry **dst;
+
+	read_cache();
+	dst = active_cache;
+	deleted = 0;
+	for (i = 0; i < active_nr; i++) {
+		struct cache_entry *ce = active_cache[i];
+		if (ce_stage(ce)) {
+			deleted++;
+			continue;
+		}
+		if (deleted)
+			*dst = ce;
+		dst++;
+	}
+	active_nr -= deleted;
+	return deleted;
+}
+
+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, reset, emu23;
 	unsigned char sha1[20];
 
-	newfd = open(".git/index.lock", 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);
-	remove_lock = 1;
 
+	merge = 0;
+	reset = 0;
+	emu23 = 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;
+		}
+
+		/* This differs from "-m" in that we'll silently ignore unmerged entries */
+		if (!strcmp(arg, "--reset")) {
+			if (stage || merge || emu23)
+				usage(read_tree_usage);
+			reset = 1;
+			merge = 1;
+			stage = 1;
+			read_cache_unmerged();
+			continue;
+		}
+
+		/* "-m" stands for "merge", meaning we start in stage 1 */
 		if (!strcmp(arg, "-m")) {
-			if (active_cache)
-				die("read-tree: cannot merge old cache on top of new");
-			if (read_cache() < 0)
-				die("read-tree: corrupt directory cache");
+			if (stage || merge || emu23)
+				usage(read_tree_usage);
+			if (read_cache_unmerged())
+				die("you need to resolve your current index first");
+			stage = 1;
+			merge = 1;
+			continue;
+		}
+
+		/* "-emu23" uses 3-way merge logic to perform fast-forward */
+		if (!strcmp(arg, "--emu23")) {
+			if (stage || merge || emu23)
+				usage(read_tree_usage);
+			if (read_cache_unmerged())
+				die("you need to resolve your current index first");
+			merge = emu23 = stage = 1;
 			continue;
 		}
-		if (get_sha1_hex(arg, sha1) < 0)
-			usage("read-tree [-m] <sha1>");
-		if (read_tree(sha1, "", 0) < 0)
+
+		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 (update && !merge)
+		usage(read_tree_usage);
+	if (merge) {
+		static const merge_fn_t merge_function[] = {
+			[1] = oneway_merge,
+			[2] = twoway_merge,
+			[3] = threeway_merge,
+		};
+		merge_fn_t fn;
+
+		if (stage < 2 || stage > 4)
+			die("just how do you expect me to merge %d trees?", stage-1);
+		if (emu23 && stage != 3)
+			die("--emu23 takes only two trees");
+		fn = merge_function[stage-1];
+		if (stage == 3 && emu23) { 
+			setup_emu23();
+			fn = merge_function[3];
+		}
+		merge_cache(active_cache, active_nr, fn);
 	}
 	if (write_cache(newfd, active_cache, active_nr) ||
-	    rename(".git/index.lock", ".git/index"))
+	    commit_index_file(&cache_file))
 		die("unable to write new index file");
-	remove_lock = 0;
 	return 0;
 }