[PATCH v1 09/11] git-gui: support using repository parent dir as a worktree

[Mark Levedahl <mlevedahl@gmail.com>]

git-gui, since 87cd09f43e ("git-gui: work from the .git dir",
2010-01-23), has had the intent to allow starting from inside a
repository, then switching to the parent directory if that is a valid
worktree.

This certainly hasn't worked since 2d92ab32fd ("rev-parse: make
--show-toplevel without a worktree an error", 2019-11-19) in git, but
breaking this git-gui feature was unintentional.

Add a proc to test if the parent of the git repository is a valid
worktree, and set that directory as the worktree if so. Use invocations
of git rev-parse to assure all validity and safety checks included in
git-core are executed.
---
 git-gui.sh | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/git-gui.sh b/git-gui.sh
index a03eaa7..e326401 100755
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -1100,6 +1100,23 @@ unset argv0dir
 ##
 ## repository setup
 
+proc is_parent_worktree {} {
+	# Directory 'parent' of a repository named 'parent/.git' might be the worktree
+	set ok 0
+	if {[file tail $::_gitdir] eq {.git}} {
+		set gitdir_parent [file join $::_gitdir {..}]
+		set expected_worktree [file normalize $gitdir_parent]
+		catch {set git_worktree [git -C $gitdir_parent rev-parse --show-toplevel]}
+		if {[string compare $expected_worktree $git_worktree] == 0} {
+			set ::_prefix {}
+			set ::_gitworktree $git_worktree
+			cd $git_worktree
+			set ok 1
+		}
+	}
+	return $ok
+}
+
 proc is_gitvars_error {err} {
 	set havevars 0
 	set GIT_DIR {}
-- 
2.54.0.99.14