Better error message when we are unable to lock the index file

Most of the callers except the one in refs.c use the function to
update the index file.  Among the index writers, everybody
except write-tree dies if they cannot open it for writing.

This gives the function an extra argument, to tell it to die
when it cannot create a new file as the lockfile.

The only caller that does not have to die is write-tree, because
updating the index for the cache-tree part is optional and not
being able to do so does not affect the correctness.  I think we
do not have to be so careful and make the failure into die() the
same way as other callers, but that would be a different patch.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

builtin-add.c

@@ -93,9 +93,7 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 
 	git_config(git_default_config);
 
-	newfd = hold_lock_file_for_update(&lock_file, get_index_file());
-	if (newfd < 0)
-		die("unable to create new index file");
+	newfd = hold_lock_file_for_update(&lock_file, get_index_file(), 1);
 
 	if (read_cache() < 0)
 		die("index file corrupt");

builtin-apply.c

@@ -2234,12 +2234,9 @@ static int apply_patch(int fd, const char *filename,
 		apply = 0;
 
 	write_index = check_index && apply;
-	if (write_index && newfd < 0) {
+	if (write_index && newfd < 0)
 		newfd = hold_lock_file_for_update(&lock_file,
-						  get_index_file());
-		if (newfd < 0)
-			die("unable to create new index file");
-	}
+						  get_index_file(), 1);
 	if (check_index) {
 		if (read_cache() < 0)
 			die("unable to read index file");

builtin-mv.c

@@ -72,10 +72,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 
 	git_config(git_default_config);
 
-	newfd = hold_lock_file_for_update(&lock_file, get_index_file());
-	if (newfd < 0)
-		die("unable to create new index file");
-
+	newfd = hold_lock_file_for_update(&lock_file, get_index_file(), 1);
 	if (read_cache() < 0)
 		die("index file corrupt");
 

builtin-read-tree.c

@@ -884,9 +884,7 @@ int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
 
 	git_config(git_default_config);
 
-	newfd = hold_lock_file_for_update(&lock_file, get_index_file());
-	if (newfd < 0)
-		die("unable to create new index file");
+	newfd = hold_lock_file_for_update(&lock_file, get_index_file(), 1);
 
 	git_config(git_default_config);
 

builtin-rm.c

@@ -52,9 +52,7 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 
 	git_config(git_default_config);
 
-	newfd = hold_lock_file_for_update(&lock_file, get_index_file());
-	if (newfd < 0)
-		die("unable to create new index file");
+	newfd = hold_lock_file_for_update(&lock_file, get_index_file(), 1);
 
 	if (read_cache() < 0)
 		die("index file corrupt");

builtin-update-index.c

@@ -491,9 +491,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 	/* We can't free this memory, it becomes part of a linked list parsed atexit() */
 	lock_file = xcalloc(1, sizeof(struct lock_file));
 
-	newfd = hold_lock_file_for_update(lock_file, get_index_file());
-	if (newfd < 0)
-		die("unable to create new cachefile");
+	newfd = hold_lock_file_for_update(lock_file, get_index_file(), 1);
 
 	entries = read_cache();
 	if (entries < 0)

builtin-write-tree.c

@@ -18,7 +18,7 @@ int write_tree(unsigned char *sha1, int missing_ok, const char *prefix)
 	/* 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_lock_file_for_update(lock_file, get_index_file());
+	newfd = hold_lock_file_for_update(lock_file, get_index_file(), 0);
 
 	entries = read_cache();
 	if (entries < 0)

cache.h

@@ -175,7 +175,7 @@ struct lock_file {
 	struct lock_file *next;
 	char filename[PATH_MAX];
 };
-extern int hold_lock_file_for_update(struct lock_file *, const char *path);
+extern int hold_lock_file_for_update(struct lock_file *, const char *path, int);
 extern int commit_lock_file(struct lock_file *);
 extern void rollback_lock_file(struct lock_file *);
 

checkout-index.c

@@ -206,7 +206,7 @@ int main(int argc, char **argv)
 			state.refresh_cache = 1;
 			if (newfd < 0)
 				newfd = hold_lock_file_for_update
-					(&lock_file, get_index_file());
+					(&lock_file, get_index_file(), 1);
 			if (newfd < 0)
 				die("cannot open index.lock file.");
 			continue;

lockfile.c

@@ -22,7 +22,7 @@ static void remove_lock_file_on_signal(int signo)
 	raise(signo);
 }
 
-int hold_lock_file_for_update(struct lock_file *lk, const char *path)
+static int lock_file(struct lock_file *lk, const char *path)
 {
 	int fd;
 	sprintf(lk->filename, "%s.lock", path);
@@ -41,6 +41,14 @@ int hold_lock_file_for_update(struct lock_file *lk, const char *path)
 	return fd;
 }
 
+int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on_error)
+{
+	int fd = lock_file(lk, path);
+	if (fd < 0 && die_on_error)
+		die("unable to create '%s': %s", path, strerror(errno));
+	return fd;
+}
+
 int commit_lock_file(struct lock_file *lk)
 {
 	char result_file[PATH_MAX];

refs.c

@@ -319,13 +319,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *path,
 
 	if (safe_create_leading_directories(lock->ref_file))
 		die("unable to create directory for %s", lock->ref_file);
-	lock->lock_fd = hold_lock_file_for_update(lock->lk, lock->ref_file);
-	if (lock->lock_fd < 0) {
-		error("Couldn't open lock file %s: %s",
-		      lock->lk->filename, strerror(errno));
-		unlock_ref(lock);
-		return NULL;
-	}
+	lock->lock_fd = hold_lock_file_for_update(lock->lk, lock->ref_file, 1);
 
 	return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
 }