[PATCH 0/2] worktree: change to new worktree dir before running hook(s)

This patch series replaces "worktree: set worktree environment in post-checkout hook"[1] from Lars, which is a proposed bug fix for ade546be47 (worktree: invoke post-checkout hook, 2017-12-07).

The problem that patch addresses is that "git worktree add" does not provide proper context to the invoked 'post-checkout' hook, so the hook doesn't know where the newly-created worktree is. Lars's approach was to set GIT_WORK_TREE to point at the new worktree directory, however, doing so has a few drawbacks:

1. GIT_WORK_TREE is normally assigned in conjunction with GIT_DIR; it is
   unusual and possibly problematic to set one but not the other.

2. Assigning GIT_WORK_TREE unconditionally may lead to unforeseen
   interactions and problems with end-user scripts and aliases or even
   within Git itself. It seems better to avoid unconditional assignment
   rather than risk problems such as those described and worked around
   by 86d26f240f (setup.c: re-fix d95138e (setup: set env $GIT_WORK_TREE
   when .., 2015-12-20)

3. Assigning GIT_WORK_TREE is too specialized a solution; it "fixes"
   only Git commands run by the hook, but does nothing for other
   commands ('mv', 'cp', etc.) that the hook might invoke.

The real problem with ade546be47 is that it neglects to change to the directory of the newly-created worktree before running the hook, thus the hook incorrectly runs in the directory in which "git worktree add" was invoked. Rather than messing with GIT_WORK_TREE, this replacement patch series fixes the problem by ensuring that the directory is changed before the hook is invoked.

[1]: https://public-inbox.org/git/20180210010132.33629-1-lars.schneider@autodesk.com/

Eric Sunshine (2):
  run-command: teach 'run_hook' about alternate worktrees
  worktree: add: change to new worktree directory before running hook

 builtin/worktree.c      | 11 ++++++++---
 run-command.c           | 23 +++++++++++++++++++++--
 run-command.h           |  4 ++++
 t/t2025-worktree-add.sh | 25 ++++++++++++++++++++++---
 4 files changed, 55 insertions(+), 8 deletions(-)