This avoids the following misleading error message:

error: unable to create temporary sha1 filename ./objects/15: File exists

mkstemp can fail for many reasons, one of which, ENOENT, can occur if
the directory for the temp file doesn't exist. create_tmpfile tried to
handle this case by always trying to mkdir the directory, even if it
already existed. This caused errno to be clobbered, so one cannot tell
why mkstemp really failed, and it truncated the buffer to just the
directory name, resulting in the strange error message shown above.

Note that in both occasions that I've seen this failure, it has not been
due to a missing directory, or bad permissions, but some other, unknown
mkstemp failure mode that did not occur when I ran git again. This code
could perhaps be made more robust by retrying mkstemp, in case it was a
transient failure.

Signed-off-by: Joey Hess <joey@kitenet.net>
---
 sha1_file.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/sha1_file.c b/sha1_file.c
index ab2b520..927fb64 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -2231,7 +2231,7 @@ static int create_tmpfile(char *buffer, size_t bufsiz, const char *filename)
 	memcpy(buffer, filename, dirlen);
 	strcpy(buffer + dirlen, "tmp_obj_XXXXXX");
 	fd = mkstemp(buffer);
-	if (fd < 0 && dirlen) {
+	if (fd < 0 && dirlen && errno == ENOENT) {
 		/* Make sure the directory exists */
 		memcpy(buffer, filename, dirlen);
 		buffer[dirlen-1] = 0;
-- 
1.5.6.5
--

[ message continues ]

Actually, it was due to bad permissions. :-) Once git was fixed to
actually say that, I figured out where to look to fix them.

--=20
see shy jo
[ message continues ]

This is strange since write_loose_object() which calls create_tmpfile()
checks for EPERM.  Perhaps this should be done in create_tmpfile()?
--

[ message continues ]

errno is clobbered by the mkdir in create_tmpfile(), that's what my patch
corrects.

I suspect that in my case, mkstemp failed with EACCES, not EPERM. git
was running as a group that did not have write access to (some) object
directories.

--=20
see shy jo
[ message continues ]