Re: [PATCH v3 3/3] worktree: make add <path> dwim

Currently 'git worktree add <path>' creates a new branch named after the
basename of the <path>, that matches the HEAD of whichever worktree we
were on when calling "git worktree add <path>".

Make 'git worktree add <path> behave more like the dwim machinery in
'git checkout <new-branch>', i.e. check if the new branch name uniquely
matches the branch name of a remote tracking branch, and if so check out
that branch and set the upstream to the remote tracking branch.

This is a change of behaviour compared to the current behaviour, where
we create a new branch matching HEAD.  However as 'git worktree' is
still an experimental feature, and it's easy to notice/correct the
behaviour in case it's not what the user desired it's probably okay to
break existing behaviour here.

In order to also satisfy users who want the current behaviour of
creating a new branch from HEAD, add a '--no-track' flag, which disables
the new behaviour, and keeps the old behaviour of creating a new branch
from the head of the current worktree.

Signed-off-by: Thomas Gummerer <redacted>
---

diff --git a/Documentation/git-worktree.txt b/Documentation/git-worktree.txt

@@ -60,9 +60,18 @@ $ git worktree add -b <branch> <path> <remote>/<branch>
 ------------
 If `<branch>` is omitted and neither `-b` nor `-B` nor `--detach` used,
-then, as a convenience, a new branch based at HEAD is created automatically,
-as if `-b $(basename <path>)` was specified.
-
+then, as a convenience, if there exists a tracking branch in exactly
+one remote (call it <remote>) matching the basename of the path
+(call it <branch>), treat it as equivalent to

 List details of each worktree.  The main worktree is listed first, followed by

diff --git a/builtin/worktree.c b/builtin/worktree.c

@@ -351,6 +352,7 @@ static int add(int ac, const char **av, const char *prefix)
+               OPT_BOOL(0, "track", &track_dwim, N_("checkout upstream branch if there's a unique match")),

                OPT_END()
        };

diff --git a/t/t2025-worktree-add.sh b/t/t2025-worktree-add.sh

@@ -360,4 +360,64 @@ test_expect_success '"add" <path> <branch> dwims' '
+test_expect_success 'git worktree add --no-track does not set up tracking' '
+       test_when_finished rm -rf repo_a &&
+       test_when_finished rm -rf repo_b &&
+       test_when_finished rm -rf foo &&
+       git init repo_a &&
+       (
+               cd repo_a &&
+               test_commit a_master &&
+               git checkout -b foo &&
+               test_commit a_foo
+       ) &&
+       git init repo_b &&
+       (
+               cd repo_b &&
+               test_commit b_master &&
+               git remote add repo_a ../repo_a &&
+               git config remote.repo_a.fetch \
+                       "+refs/heads/*:refs/remotes/other_a/*" &&
+               git fetch --all &&
+               git worktree add --no-track ../foo
+       ) &&
+       (
+               cd foo &&
+               ! test_branch_upstream foo repo_a foo &&
+               git rev-parse other_a/foo >expect &&
+               git rev-parse foo >actual &&
+               ! test_cmp expect actual
+       )
+'