[PATCH v2] refs: print errno for read_raw_ref if GIT_TRACE_REFS is set

From: Han-Wen Nienhuys <hanwen@google.com>

The ref backend API uses errno as a sideband error channel.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
---
    refs: print errno for read_raw_ref if GIT_TRACE_REFS is set
    
    The ref backend API uses errno as a sideband error channel.
    
    Signed-off-by: Han-Wen Nienhuys hanwen@google.com

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1002%2Fhanwen%2Ferrno-debug-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1002/hanwen/errno-debug-v2
Pull-Request: https://github.com/git/git/pull/1002

Range-diff vs v1:

 1:  9b150c5563f9 ! 1:  1e9a8990e7f2 refs: print errno for read_raw_ref if GIT_TRACE_REFS is set
     @@ Commit message
      
       ## refs/debug.c ##
      @@ refs/debug.c: static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
     + {
     + 	struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
       	int res = 0;
     ++	int saved_errno = 0;
       
       	oidcpy(oid, &null_oid);
      +	errno = 0;
       	res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
       					    type);
     ++	saved_errno = errno;
       
     -@@ refs/debug.c: static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
     + 	if (res == 0) {
       		trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
       			refname, oid_to_hex(oid), referent->buf, *type, res);
       	} else {
      -		trace_printf_key(&trace_refs, "read_raw_ref: %s: %d\n", refname, res);
      +		trace_printf_key(&trace_refs,
      +				 "read_raw_ref: %s: %d (errno %d)\n", refname,
     -+				 res, errno);
     ++				 res, saved_errno);
       	}
       	return res;
       }

 refs/debug.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)