worktree: check if a submodule uses worktrees

In a later patch we want to move around the the git directory of
a submodule. Both submodules as well as worktrees are involved in
placing git directories at unusual places, so their functionality
may collide. To react appropriately to situations where worktrees
in submodules are in use, offer a new function to query the
a submodule if it uses the worktree feature.

An earlier approach:
"Implement submodule_get_worktrees and just count them", however:
This can be done cheaply (both in new code to write as well as run time)
by obtaining the list of worktrees based off that submodules git
directory. However as we have loaded the variables for the current
repository, the values in the submodule worktree
can be wrong, e.g.
* core.ignorecase may differ between these two repositories
* the ref resolution is broken (refs/heads/branch in the submodule
resolves to the sha1 value of the `branch` in the current repository
that may not exist or have another sha1)

The implementation here is just checking for any files in
$GIT_COMMON_DIR/worktrees for the submodule, which ought to be sufficient
if the submodule is using the current repository format, which we also
check.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/worktree.c b/worktree.c
index eb6121263b0d56b6b7ea7c5024e9ceb68256c1c5..d4606aa8cd5ab476599a2f91f9d96ae03389fbab 100644 (file)
--- a/worktree.c
+++ b/worktree.c
@@ -380,3 +380,53 @@ const struct worktree *find_shared_symref(const char *symref,
 
        return existing;
 }
+
+int submodule_uses_worktrees(const char *path)
+{
+       char *submodule_gitdir;
+       struct strbuf sb = STRBUF_INIT;
+       DIR *dir;
+       struct dirent *d;
+       int ret;
+       struct repository_format format;
+
+       submodule_gitdir = git_pathdup_submodule(path, "%s", "");
+       if (!submodule_gitdir)
+               return 0;
+
+       /* The env would be set for the superproject. */
+       get_common_dir_noenv(&sb, submodule_gitdir);
+
+       /*
+        * The check below is only known to be good for repository format
+        * version 0 at the time of writing this code.
+        */
+       strbuf_addstr(&sb, "/config");
+       read_repository_format(&format, sb.buf);
+       if (format.version != 0) {
+               strbuf_release(&sb);
+               return 1;
+       }
+
+       /* Replace config by worktrees. */
+       strbuf_setlen(&sb, sb.len - strlen("config"));
+       strbuf_addstr(&sb, "worktrees");
+
+       /* See if there is any file inside the worktrees directory. */
+       dir = opendir(sb.buf);
+       strbuf_release(&sb);
+       free(submodule_gitdir);
+
+       if (!dir)
+               return 0;
+
+       while ((d = readdir(dir)) != NULL) {
+               if (is_dot_or_dotdot(d->d_name))
+                       continue;
+
+               ret = 1;
+               break;
+       }
+       closedir(dir);
+       return ret;
+}

diff --git a/worktree.h b/worktree.h
index d59ce1fee875800462a1e464592fd9dd01828e17..6bfb985203070e3051f82348568840f5577bf0dc 100644 (file)
--- a/worktree.h
+++ b/worktree.h
@@ -27,6 +27,11 @@ struct worktree {
  */
 extern struct worktree **get_worktrees(unsigned flags);
 
+/*
+ * Returns 1 if linked worktrees exist, 0 otherwise.
+ */
+extern int submodule_uses_worktrees(const char *path);
+
 /*
  * Return git dir of the worktree. Note that the path may be relative.
  * If wt is NULL, git dir of current worktree is returned.