[RFC PATCH 1/1] dir: consider worktree config in path recursion

[Goss Geppert <gg.oss.dev@gmail.com>]

Since 8d92fb2927 (dir: replace exponential algorithm with a linear one,
2020-04-01) the following no longer works:

    1) Initialize a repository.
    2) Set the `core.worktree` location to a parent directory of the
       default worktree.
    3) Add a file located in the default worktree location to the index
       (i.e. anywhere in the immediate parent directory of the gitdir).

This commit adds a check to determine whether a nested repository that
is encountered in recursing a path is actually `the_repository`.  If so,
simply treat the directory as if it doesn't contain a nested repository.

Prior to this commit, the `add` operation was silently ignored.
---
 dir.c | 37 ++++++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/dir.c b/dir.c
index f2b0f24210..cef39f43d8 100644
--- a/dir.c
+++ b/dir.c
@@ -1861,7 +1861,7 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
 	 */
 	enum path_treatment state;
 	int matches_how = 0;
-	int nested_repo = 0, check_only, stop_early;
+	int check_only, stop_early;
 	int old_ignored_nr, old_untracked_nr;
 	/* The "len-1" is to strip the final '/' */
 	enum exist_status status = directory_exists_in_index(istate, dirname, len-1);
@@ -1893,16 +1893,39 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
 
 	if ((dir->flags & DIR_SKIP_NESTED_GIT) ||
 		!(dir->flags & DIR_NO_GITLINKS)) {
+		/*
+		 * Determine if `dirname` is a nested repo by confirming that:
+		 * 1) we are in a nonbare repository, and
+		 * 2) `dirname` is not an immediate parent of `the_repository->gitdir`,
+		 *    which could occur if the `worktree` location was manually
+		 *    configured by the user
+		 */
+		int nested_repo;
 		struct strbuf sb = STRBUF_INIT;
 		strbuf_addstr(&sb, dirname);
 		nested_repo = is_nonbare_repository_dir(&sb);
+
+		if (nested_repo) {
+			char *real_dirname, *real_gitdir;
+			strbuf_reset(&sb);
+			strbuf_addstr(&sb, dirname);
+			strbuf_complete(&sb, '/');
+			strbuf_addstr(&sb, ".git");
+			real_dirname = real_pathdup(sb.buf, 0);
+			real_gitdir = real_pathdup(the_repository->gitdir, 0);
+
+			nested_repo = !!strcmp(real_dirname, real_gitdir);
+			free(real_gitdir);
+			free(real_dirname);
+		}
 		strbuf_release(&sb);
-	}
-	if (nested_repo) {
-		if ((dir->flags & DIR_SKIP_NESTED_GIT) ||
-		    (matches_how == MATCHED_RECURSIVELY_LEADING_PATHSPEC))
-			return path_none;
-		return excluded ? path_excluded : path_untracked;
+
+		if (nested_repo) {
+			if ((dir->flags & DIR_SKIP_NESTED_GIT) ||
+				(matches_how == MATCHED_RECURSIVELY_LEADING_PATHSPEC))
+				return path_none;
+			return excluded ? path_excluded : path_untracked;
+		}
 	}
 
 	if (!(dir->flags & DIR_SHOW_OTHER_DIRECTORIES)) {
-- 
2.36.0