Merge branch 'jk/shallow-update-fix'

Serving objects from a shallow repository needs to write a
new file to hold the temporary shallow boundaries but it was not
cleaned when we exit due to die() or a signal.

* jk/shallow-update-fix:
  shallow: verify shallow file after taking lock
  shallow: automatically clean up shallow tempfiles
  shallow: use stat_validity to check for up-to-date file

Author: gitster

builtin/receive-pack.c

@@ -828,14 +828,10 @@ static void execute_commands(struct command *commands,
 		}
 	}
 
-	if (shallow_update) {
-		if (!checked_connectivity)
-			error("BUG: run 'git fsck' for safety.\n"
-			      "If there are errors, try to remove "
-			      "the reported refs above");
-		if (alt_shallow_file && *alt_shallow_file)
-			unlink(alt_shallow_file);
-	}
+	if (shallow_update && !checked_connectivity)
+		error("BUG: run 'git fsck' for safety.\n"
+		      "If there are errors, try to remove "
+		      "the reported refs above");
 }
 
 static struct command *read_head_info(struct sha1_array *shallow)
@@ -1087,10 +1083,6 @@ static void update_shallow_info(struct command *commands,
 			cmd->skip_update = 1;
 		}
 	}
-	if (alt_shallow_file && *alt_shallow_file) {
-		unlink(alt_shallow_file);
-		alt_shallow_file = NULL;
-	}
 	free(ref_status);
 }
 

commit.h

@@ -209,7 +209,7 @@ extern int write_shallow_commits(struct strbuf *out, int use_pack_protocol,
 extern void setup_alternate_shallow(struct lock_file *shallow_lock,
 				    const char **alternate_shallow_file,
 				    const struct sha1_array *extra);
-extern char *setup_temporary_shallow(const struct sha1_array *extra);
+extern const char *setup_temporary_shallow(const struct sha1_array *extra);
 extern void advertise_shallow_grafts(int);
 
 struct shallow_info {

fetch-pack.c

@@ -948,17 +948,6 @@ static void update_shallow(struct fetch_pack_args *args,
 	if (!si->shallow || !si->shallow->nr)
 		return;
 
-	if (alternate_shallow_file) {
-		/*
-		 * The temporary shallow file is only useful for
-		 * index-pack and unpack-objects because it may
-		 * contain more roots than we want. Delete it.
-		 */
-		if (*alternate_shallow_file)
-			unlink(alternate_shallow_file);
-		free((char *)alternate_shallow_file);
-	}
-
 	if (args->cloning) {
 		/*
 		 * remote is shallow, but this is a clone, there are

shallow.c

@@ -8,9 +8,10 @@
 #include "diff.h"
 #include "revision.h"
 #include "commit-slab.h"
+#include "sigchain.h"
 
 static int is_shallow = -1;
-static struct stat shallow_stat;
+static struct stat_validity shallow_stat;
 static char *alternate_shallow_file;
 
 void set_alternate_shallow_file(const char *path, int override)
@@ -52,12 +53,12 @@ int is_repository_shallow(void)
 	 * shallow file should be used. We could just open it and it
 	 * will likely fail. But let's do an explicit check instead.
 	 */
-	if (!*path ||
-	    stat(path, &shallow_stat) ||
-	    (fp = fopen(path, "r")) == NULL) {
+	if (!*path || (fp = fopen(path, "r")) == NULL) {
+		stat_validity_clear(&shallow_stat);
 		is_shallow = 0;
 		return is_shallow;
 	}
+	stat_validity_update(&shallow_stat, fileno(fp));
 	is_shallow = 1;
 
 	while (fgets(buf, sizeof(buf), fp)) {
@@ -137,21 +138,11 @@ struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 
 void check_shallow_file_for_update(void)
 {
-	struct stat st;
-
-	if (!is_shallow)
-		return;
-	else if (is_shallow == -1)
+	if (is_shallow == -1)
 		die("BUG: shallow must be initialized by now");
 
-	if (stat(git_path("shallow"), &st))
-		die("shallow file was removed during fetch");
-	else if (st.st_mtime != shallow_stat.st_mtime
-#ifdef USE_NSEC
-		 || ST_MTIME_NSEC(st) != ST_MTIME_NSEC(shallow_stat)
-#endif
-		   )
-		die("shallow file was changed during fetch");
+	if (!stat_validity_check(&shallow_stat, git_path("shallow")))
+		die("shallow file has changed since we read it");
 }
 
 #define SEEN_ONLY 1
@@ -216,27 +207,53 @@ int write_shallow_commits(struct strbuf *out, int use_pack_protocol,
 	return write_shallow_commits_1(out, use_pack_protocol, extra, 0);
 }
 
-char *setup_temporary_shallow(const struct sha1_array *extra)
+static struct strbuf temporary_shallow = STRBUF_INIT;
+
+static void remove_temporary_shallow(void)
+{
+	if (temporary_shallow.len) {
+		unlink_or_warn(temporary_shallow.buf);
+		strbuf_reset(&temporary_shallow);
+	}
+}
+
+static void remove_temporary_shallow_on_signal(int signo)
+{
+	remove_temporary_shallow();
+	sigchain_pop(signo);
+	raise(signo);
+}
+
+const char *setup_temporary_shallow(const struct sha1_array *extra)
 {
+	static int installed_handler;
 	struct strbuf sb = STRBUF_INIT;
 	int fd;
 
+	if (temporary_shallow.len)
+		die("BUG: attempt to create two temporary shallow files");
+
 	if (write_shallow_commits(&sb, 0, extra)) {
-		struct strbuf path = STRBUF_INIT;
-		strbuf_addstr(&path, git_path("shallow_XXXXXX"));
-		fd = xmkstemp(path.buf);
+		strbuf_addstr(&temporary_shallow, git_path("shallow_XXXXXX"));
+		fd = xmkstemp(temporary_shallow.buf);
+
+		if (!installed_handler) {
+			atexit(remove_temporary_shallow);
+			sigchain_push_common(remove_temporary_shallow_on_signal);
+		}
+
 		if (write_in_full(fd, sb.buf, sb.len) != sb.len)
 			die_errno("failed to write to %s",
-				  path.buf);
+				  temporary_shallow.buf);
 		close(fd);
 		strbuf_release(&sb);
-		return strbuf_detach(&path, NULL);
+		return temporary_shallow.buf;
 	}
 	/*
 	 * is_repository_shallow() sees empty string as "no shallow
 	 * file".
 	 */
-	return xstrdup("");
+	return temporary_shallow.buf;
 }
 
 void setup_alternate_shallow(struct lock_file *shallow_lock,
@@ -246,9 +263,9 @@ void setup_alternate_shallow(struct lock_file *shallow_lock,
 	struct strbuf sb = STRBUF_INIT;
 	int fd;
 
-	check_shallow_file_for_update();
 	fd = hold_lock_file_for_update(shallow_lock, git_path("shallow"),
 				       LOCK_DIE_ON_ERROR);
+	check_shallow_file_for_update();
 	if (write_shallow_commits(&sb, 0, extra)) {
 		if (write_in_full(fd, sb.buf, sb.len) != sb.len)
 			die_errno("failed to write to %s",
@@ -293,9 +310,9 @@ void prune_shallow(int show_only)
 		strbuf_release(&sb);
 		return;
 	}
-	check_shallow_file_for_update();
 	fd = hold_lock_file_for_update(&shallow_lock, git_path("shallow"),
 				       LOCK_DIE_ON_ERROR);
+	check_shallow_file_for_update();
 	if (write_shallow_commits_1(&sb, 0, NULL, SEEN_ONLY)) {
 		if (write_in_full(fd, sb.buf, sb.len) != sb.len)
 			die_errno("failed to write to %s",

upload-pack.c

@@ -81,7 +81,7 @@ static void create_pack_file(void)
 	const char *argv[12];
 	int i, arg = 0;
 	FILE *pipe_fd;
-	char *shallow_file = NULL;
+	const char *shallow_file = NULL;
 
 	if (shallow_nr) {
 		shallow_file = setup_temporary_shallow(NULL);
@@ -242,11 +242,6 @@ static void create_pack_file(void)
 		error("git upload-pack: git-pack-objects died with error.");
 		goto fail;
 	}
-	if (shallow_file) {
-		if (*shallow_file)
-			unlink(shallow_file);
-		free(shallow_file);
-	}
 
 	/* flush the data */
 	if (0 <= buffered) {