More friendly message when locking the index fails.

Just saying that index.lock exists doesn't tell the user _what_ to do
to fix the problem. We should give an indication that it's normally
safe to delete index.lock after making sure git isn't running here.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/lockfile.c b/lockfile.c
index 8589155532..8e556ff8c9 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -158,11 +158,25 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
 	return lk->fd;
 }
 
+
+NORETURN void unable_to_lock_index_die(const char *path, int err)
+{
+	if (errno == EEXIST) {
+		die("Unable to create '%s.lock': %s.\n\n"
+		    "If no other git process is currently running, this probably means a\n"
+		    "git process crashed in this repository earlier. Make sure no other git\n"
+		    "process is running and remove the file manually to continue.",
+		    path, strerror(err));
+	} else {
+		die("Unable to create '%s.lock': %s", path, strerror(err));
+	}
+}
+
 int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags)
 {
 	int fd = lock_file(lk, path, flags);
 	if (fd < 0 && (flags & LOCK_DIE_ON_ERROR))
-		die("unable to create '%s.lock': %s", path, strerror(errno));
+		unable_to_lock_index_die(path, errno);
 	return fd;
 }