Make error messages from cherry-pick/revert more sensible

The original "rewrite in C" did somewhat a sloppy job while
stealing code from git-write-tree.

The caller pretends as if the write_tree() function would return
an error code and being able to issue a sensible error message
itself, but write_tree() function just calls die() and never
returns an error.  Worse yet, the function claims that it was
running git-write-tree (which is no longer true after
cherry-pick stole it).

Tested-by: Björn Steinbrink <B.Steinbrink@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 16 insertions, 55 deletions

diff --git a/builtin-write-tree.c b/builtin-write-tree.c
index d16b9ed009..e838d01233 100644
--- a/builtin-write-tree.c
+++ b/builtin-write-tree.c
@@ -11,63 +11,12 @@
 static const char write_tree_usage[] =
 "git-write-tree [--missing-ok] [--prefix=<prefix>/]";
 
-int write_tree(unsigned char *sha1, int missing_ok, const char *prefix)
-{
-	int entries, was_valid, newfd;
-
-	/* We can't free this memory, it becomes part of a linked list parsed atexit() */
-	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
-
-	newfd = hold_locked_index(lock_file, 1);
-
-	entries = read_cache();
-	if (entries < 0)
-		die("git-write-tree: error reading cache");
-
-	if (!active_cache_tree)
-		active_cache_tree = cache_tree();
-
-	was_valid = cache_tree_fully_valid(active_cache_tree);
-
-	if (!was_valid) {
-		if (cache_tree_update(active_cache_tree,
-				      active_cache, active_nr,
-				      missing_ok, 0) < 0)
-			die("git-write-tree: error building trees");
-		if (0 <= newfd) {
-			if (!write_cache(newfd, active_cache, active_nr) &&
-			    !commit_lock_file(lock_file))
-				newfd = -1;
-		}
-		/* Not being able to write is fine -- we are only interested
-		 * in updating the cache-tree part, and if the next caller
-		 * ends up using the old index with unupdated cache-tree part
-		 * it misses the work we did here, but that is just a
-		 * performance penalty and not a big deal.
-		 */
-	}
-
-	if (prefix) {
-		struct cache_tree *subtree =
-			cache_tree_find(active_cache_tree, prefix);
-		if (!subtree)
-			die("git-write-tree: prefix %s not found", prefix);
-		hashcpy(sha1, subtree->sha1);
-	}
-	else
-		hashcpy(sha1, active_cache_tree->sha1);
-
-	if (0 <= newfd)
-		rollback_lock_file(lock_file);
-
-	return 0;
-}
-
 int cmd_write_tree(int argc, const char **argv, const char *unused_prefix)
 {
 	int missing_ok = 0, ret;
 	const char *prefix = NULL;
 	unsigned char sha1[20];
+	const char *me = "git-write-tree";
 
 	git_config(git_default_config);
 	while (1 < argc) {
@@ -84,8 +33,20 @@ int cmd_write_tree(int argc, const char **argv, const char *unused_prefix)
 	if (argc > 2)
 		die("too many options");
 
-	ret = write_tree(sha1, missing_ok, prefix);
-	printf("%s\n", sha1_to_hex(sha1));
-
+	ret = write_cache_as_tree(sha1, missing_ok, prefix);
+	switch (ret) {
+	case 0:
+		printf("%s\n", sha1_to_hex(sha1));
+		break;
+	case WRITE_TREE_UNREADABLE_INDEX:
+		die("%s: error reading the index", me);
+		break;
+	case WRITE_TREE_UNMERGED_INDEX:
+		die("%s: error building trees; the index is unmerged?", me);
+		break;
+	case WRITE_TREE_PREFIX_ERROR:
+		die("%s: prefix %s not found", me, prefix);
+		break;
+	}
 	return ret;
 }