sha1_file: remove static strbuf from sha1_file_name()

Using a static buffer in sha1_file_name() is error prone
and the performance improvements it gives are not needed
in many of the callers.

So let's get rid of this static buffer and, if necessary
or helpful, let's use one in the caller.

Suggested-by: Jeff Hostetler <git@jeffhostetler.com>
Helped-by: Kevin Daudt <me@ikke.info>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -902,12 +902,10 @@ extern void check_repository_format(void);
 #define TYPE_CHANGED    0x0040
 
 /*
- * Return the name of the file in the local object database that would
- * be used to store a loose object with the specified sha1.  The
- * return value is a pointer to a statically allocated buffer that is
- * overwritten each time the function is called.
+ * Put in `buf` the name of the file in the local object database that
+ * would be used to store a loose object with the specified sha1.
  */
-extern const char *sha1_file_name(const unsigned char *sha1);
+extern void sha1_file_name(struct strbuf *buf, const unsigned char *sha1);
 
 /*
  * Return an abbreviated sha1 unique within this repository's object database.

http-walker.c

@@ -544,8 +544,10 @@ static int fetch_object(struct walker *walker, unsigned char *sha1)
 	} else if (hashcmp(obj_req->sha1, req->real_sha1)) {
 		ret = error("File %s has bad hash", hex);
 	} else if (req->rename < 0) {
-		ret = error("unable to write sha1 filename %s",
-			    sha1_file_name(req->sha1));
+		struct strbuf buf = STRBUF_INIT;
+		sha1_file_name(&buf, req->sha1);
+		ret = error("unable to write sha1 filename %s", buf.buf);
+		strbuf_release(&buf);
 	}
 
 	release_http_object_request(req);

http.c

@@ -2150,7 +2150,7 @@ struct http_object_request *new_http_object_request(const char *base_url,
 	unsigned char *sha1)
 {
 	char *hex = sha1_to_hex(sha1);
-	const char *filename;
+	struct strbuf filename = STRBUF_INIT;
 	char prevfile[PATH_MAX];
 	int prevlocal;
 	char prev_buf[PREV_BUF_SIZE];
@@ -2162,14 +2162,15 @@ struct http_object_request *new_http_object_request(const char *base_url,
 	hashcpy(freq->sha1, sha1);
 	freq->localfile = -1;
 
-	filename = sha1_file_name(sha1);
+	sha1_file_name(&filename, sha1);
 	snprintf(freq->tmpfile, sizeof(freq->tmpfile),
-		 "%s.temp", filename);
+		 "%s.temp", filename.buf);
 
-	snprintf(prevfile, sizeof(prevfile), "%s.prev", filename);
+	snprintf(prevfile, sizeof(prevfile), "%s.prev", filename.buf);
 	unlink_or_warn(prevfile);
 	rename(freq->tmpfile, prevfile);
 	unlink_or_warn(freq->tmpfile);
+	strbuf_release(&filename);
 
 	if (freq->localfile != -1)
 		error("fd leakage in start: %d", freq->localfile);
@@ -2284,6 +2285,7 @@ void process_http_object_request(struct http_object_request *freq)
 int finish_http_object_request(struct http_object_request *freq)
 {
 	struct stat st;
+	struct strbuf filename = STRBUF_INIT;
 
 	close(freq->localfile);
 	freq->localfile = -1;
@@ -2309,8 +2311,10 @@ int finish_http_object_request(struct http_object_request *freq)
 		unlink_or_warn(freq->tmpfile);
 		return -1;
 	}
-	freq->rename =
-		finalize_object_file(freq->tmpfile, sha1_file_name(freq->sha1));
+
+	sha1_file_name(&filename, freq->sha1);
+	freq->rename = finalize_object_file(freq->tmpfile, filename.buf);
+	strbuf_release(&filename);
 
 	return freq->rename;
 }

sha1_file.c

@@ -251,15 +251,11 @@ static void fill_sha1_path(struct strbuf *buf, const unsigned char *sha1)
 	}
 }
 
-const char *sha1_file_name(const unsigned char *sha1)
+void sha1_file_name(struct strbuf *buf, const unsigned char *sha1)
 {
-	static struct strbuf buf = STRBUF_INIT;
-
-	strbuf_reset(&buf);
-	strbuf_addf(&buf, "%s/", get_object_directory());
+	strbuf_addf(buf, "%s/", get_object_directory());
 
-	fill_sha1_path(&buf, sha1);
-	return buf.buf;
+	fill_sha1_path(buf, sha1);
 }
 
 struct strbuf *alt_scratch_buf(struct alternate_object_database *alt)
@@ -643,7 +639,12 @@ int check_and_freshen_file(const char *fn, int freshen)
 
 static int check_and_freshen_local(const unsigned char *sha1, int freshen)
 {
-	return check_and_freshen_file(sha1_file_name(sha1), freshen);
+	static struct strbuf buf = STRBUF_INIT;
+
+	strbuf_reset(&buf);
+	sha1_file_name(&buf, sha1);
+
+	return check_and_freshen_file(buf.buf, freshen);
 }
 
 static int check_and_freshen_nonlocal(const unsigned char *sha1, int freshen)
@@ -799,8 +800,12 @@ static int stat_sha1_file(const unsigned char *sha1, struct stat *st,
 			  const char **path)
 {
 	struct alternate_object_database *alt;
+	static struct strbuf buf = STRBUF_INIT;
+
+	strbuf_reset(&buf);
+	sha1_file_name(&buf, sha1);
+	*path = buf.buf;
 
-	*path = sha1_file_name(sha1);
 	if (!lstat(*path, st))
 		return 0;
 
@@ -824,8 +829,12 @@ static int open_sha1_file(const unsigned char *sha1, const char **path)
 	int fd;
 	struct alternate_object_database *alt;
 	int most_interesting_errno;
+	static struct strbuf buf = STRBUF_INIT;
+
+	strbuf_reset(&buf);
+	sha1_file_name(&buf, sha1);
+	*path = buf.buf;
 
-	*path = sha1_file_name(sha1);
 	fd = git_open(*path);
 	if (fd >= 0)
 		return fd;
@@ -1487,9 +1496,12 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 	git_SHA_CTX c;
 	unsigned char parano_sha1[20];
 	static struct strbuf tmp_file = STRBUF_INIT;
-	const char *filename = sha1_file_name(sha1);
+	static struct strbuf filename = STRBUF_INIT;
+
+	strbuf_reset(&filename);
+	sha1_file_name(&filename, sha1);
 
-	fd = create_tmpfile(&tmp_file, filename);
+	fd = create_tmpfile(&tmp_file, filename.buf);
 	if (fd < 0) {
 		if (errno == EACCES)
 			return error("insufficient permission for adding an object to repository database %s", get_object_directory());
@@ -1542,7 +1554,7 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 			warning_errno("failed utime() on %s", tmp_file.buf);
 	}
 
-	return finalize_object_file(tmp_file.buf, filename);
+	return finalize_object_file(tmp_file.buf, filename.buf);
 }
 
 static int freshen_loose_object(const unsigned char *sha1)