[PATCH 1/1] commit-graph: fix UX issue when .lock file exists

[Derrick Stolee <dstolee@microsoft.com>]

The commit-graph file lives in the .git/objects/info directory.
Previously, a failure to acquire the commit-graph.lock file was
assumed to be due to the lack of the info directory, so a mkdir()
was called. This gave incorrect messaging if instead the lockfile
was open by another process:

  "fatal: cannot mkdir .git/objects/info: File exists"

Rearrange the expectations of this directory existing to avoid
this error, and instead show the typical message when a lockfile
already exists.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c | 24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index a8c337dd77..8399194da1 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1,5 +1,6 @@
 #include "cache.h"
 #include "config.h"
+#include "dir.h"
 #include "git-compat-util.h"
 #include "lockfile.h"
 #include "pack.h"
@@ -640,13 +641,13 @@ void write_commit_graph(const char *obj_dir,
 	struct hashfile *f;
 	uint32_t i, count_distinct = 0;
 	char *graph_name;
-	int fd;
 	struct lock_file lk = LOCK_INIT;
 	uint32_t chunk_ids[5];
 	uint64_t chunk_offsets[5];
 	int num_chunks;
 	int num_extra_edges;
 	struct commit_list *parent;
+	struct strbuf folder = STRBUF_INIT;
 
 	oids.nr = 0;
 	oids.alloc = approximate_object_count() / 4;
@@ -754,23 +755,14 @@ void write_commit_graph(const char *obj_dir,
 	compute_generation_numbers(&commits);
 
 	graph_name = get_commit_graph_filename(obj_dir);
-	fd = hold_lock_file_for_update(&lk, graph_name, 0);
 
-	if (fd < 0) {
-		struct strbuf folder = STRBUF_INIT;
-		strbuf_addstr(&folder, graph_name);
-		strbuf_setlen(&folder, strrchr(folder.buf, '/') - folder.buf);
-
-		if (mkdir(folder.buf, 0777) < 0)
-			die_errno(_("cannot mkdir %s"), folder.buf);
-		strbuf_release(&folder);
-
-		fd = hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
-
-		if (fd < 0)
-			die_errno("unable to create '%s'", graph_name);
-	}
+	strbuf_addstr(&folder, graph_name);
+	strbuf_setlen(&folder, strrchr(folder.buf, '/') - folder.buf);
+	if (!file_exists(folder.buf) && mkdir(folder.buf, 0777) < 0)
+		die_errno(_("cannot mkdir %s"), folder.buf);
+	strbuf_release(&folder);
 
+	hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
 	f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 
 	hashwrite_be32(f, GRAPH_SIGNATURE);
-- 
2.17.0.39.g685157f7fb