commit.c: make find_commit_subject() more robust

diff --git a/sha1_file.c b/sha1_file.c
index 0c70152c17fbf612bbdf0112bf12fe8f7a852761..99155c0d6b77aa2a772330d51fa604b1c4a9b0cf 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -377,15 +377,12 @@ void read_info_alternates(const char * relative_base, int depth)
        char *map;
        size_t mapsz;
        struct stat st;
-       const char alt_file_name[] = "info/alternates";
-       /* Given that relative_base is no longer than PATH_MAX,
-          ensure that "path" has enough space to append "/", the
-          file name, "info/alternates", and a trailing NUL.  */
-       char path[PATH_MAX + 1 + sizeof alt_file_name];
+       char *path;
        int fd;
 
-       sprintf(path, "%s/%s", relative_base, alt_file_name);
+       path = xstrfmt("%s/info/alternates", relative_base);
        fd = git_open_noatime(path);
+       free(path);
        if (fd < 0)
                return;
        if (fstat(fd, &st) || (st.st_size == 0)) {
@@ -443,6 +440,7 @@ void prepare_alt_odb(void)
        read_info_alternates(get_object_directory(), 0);
 }
 
+/* Returns 1 if we have successfully freshened the file, 0 otherwise. */
 static int freshen_file(const char *fn)
 {
        struct utimbuf t;
@@ -450,11 +448,18 @@ static int freshen_file(const char *fn)
        return !utime(fn, &t);
 }
 
+/*
+ * All of the check_and_freshen functions return 1 if the file exists and was
+ * freshened (if freshening was requested), 0 otherwise. If they return
+ * 0, you should not assume that it is safe to skip a write of the object (it
+ * either does not exist on disk, or has a stale mtime and may be subject to
+ * pruning).
+ */
 static int check_and_freshen_file(const char *fn, int freshen)
 {
        if (access(fn, F_OK))
                return 0;
-       if (freshen && freshen_file(fn))
+       if (freshen && !freshen_file(fn))
                return 0;
        return 1;
 }