[PATCH] Allow git mv FileA fILEa when core.ignorecase = true

["Torsten Bögershausen" <tboegi@web.de>]

    The typical use case is when a file "FileA" should be renamed into fILEa
    and we are on a case insenstive file system (system core.ignorecase = true).
    Source and destination are the same file, it can be accessed under both names.
    This makes git think that the destination file exists.
    Unless used with --forced, git will refuse the "git mv FileA fILEa".
    This change will allow "git mv FileA fILEa", when core.ignorecase = true
    and source and destination filenames only differ in case and the file length
    is identical.
    On Linux/Unix/Mac OS X the mv is allowed when the inode of the source and
    destination are equal.
    On  this allows renames of MÄRCHEN into Märchen on Mac OS X.
    (As a side effect, a file can be renamed to a name which is already
    hard-linked to the same inode)

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
---
 builtin/mv.c  |   20 +++++++++++++++-----
 t/t7001-mv.sh |   29 +++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/builtin/mv.c b/builtin/mv.c
index 93e8995..e0aad62 100644
--- a/builtin/mv.c
+++ b/builtin/mv.c
@@ -62,7 +62,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 	};
 	const char **source, **destination, **dest_path;
 	enum update_mode { BOTH = 0, WORKING_DIRECTORY, INDEX } *modes;
-	struct stat st;
+	struct stat st, st_dst;
 	struct string_list src_for_dst = STRING_LIST_INIT_NODUP;
 
 	git_config(git_default_config, NULL);
@@ -164,15 +164,25 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 			}
 		} else if (cache_name_pos(src, length) < 0)
 			bad = "not under version control";
-		else if (lstat(dst, &st) == 0) {
+		else if (lstat(dst, &st_dst) == 0) {
+			int allow_force = force;
 			bad = "destination exists";
-			if (force) {
+			/* Allow when src and dst have the same inode (Mac OS X) */
+			/* Allow when ignore_case and same file length (Windows) */
+			if (((st_dst.st_ino) && (st_dst.st_ino == st.st_ino)) ||
+					((ignore_case) && !strcasecmp(src, dst) &&
+					 (st.st_size == st_dst.st_size))) {
+				allow_force = 1;
+				bad = NULL;
+			}
+			if (allow_force) {
 				/*
 				 * only files can overwrite each other:
 				 * check both source and destination
 				 */
-				if (S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)) {
-					warning("%s; will overwrite!", bad);
+				if (S_ISREG(st_dst.st_mode) || S_ISLNK(st_dst.st_mode)) {
+					if (bad)
+						warning("%s; will overwrite!", bad);
 					bad = NULL;
 				} else
 					bad = "Cannot overwrite";
diff --git a/t/t7001-mv.sh b/t/t7001-mv.sh
index a845b15..d0e73ee 100755
--- a/t/t7001-mv.sh
+++ b/t/t7001-mv.sh
@@ -255,4 +255,33 @@ test_expect_success SYMLINKS 'git mv should overwrite file with a symlink' '
 
 rm -f moved symlink
 
+touch x
+if ln x y 2>/dev/null; then
+	hardlinks=1
+fi
+rm -f x y
+
+if test "$(git config --bool core.ignorecase)" = true -o "$hardlinks"; then
+	test_expect_success 'git mv FileA fILEa' '
+
+		rm -fr .git * &&
+		git init &&
+		echo FileA > FileA &&
+		git add FileA &&
+		git commit -m add FileA &&
+		{
+			if ! test -f fILEa; then
+				ln FileA fILEa
+			fi
+		} &&
+		git mv FileA fILEa &&
+		git commit -m "mv FileA fILEa" &&
+		rm -f FileA fILEa &&
+		git reset --hard &&
+		test "$(echo *)" = fILEa
+	'
+else
+	say "Neither ignorecase nor hardlinks, skipping git mv FileA fILEa"
+fi
+
 test_done
-- 
1.7.4