The `includeIf` mechanism already supports matching on the `.git`
directory path (`gitdir`) and the currently checked out branch
(`onbranch`).  But in multi-worktree setups the `.git` directory of a
linked worktree points into the main repository's `.git/worktrees/`
area, which makes `gitdir` patterns cumbersome when one wants to
include config based on the working tree's checkout path instead.

Introduce two new condition keywords:

  - `worktree:<pattern>` matches the realpath of the current worktree's
    working directory against a glob pattern.
  - `worktree/i:<pattern>` is the case-insensitive variant.

Supported pattern features: glob wildcards, `**/` and `/**`, `~`
expansion, `./` relative paths, and trailing-`/` prefix matching.
The condition never matches in a bare repository.

Signed-off-by: Chen Linxuan <redacted>
---
Changes in v6:
- Rebase onto current `master` at Git 2.55.
- Add an in-code comment explaining why the non-repository worktree
  tests use the loose `**.path` pattern (suggested by Junio C Hamano).
- Link to v5: https://lore.kernel.org/r/20260525-includeif-worktree-v5-0-1efe525d025a@black-desk.cn (local)

Changes in v5:
- Fix Windows CI failure: use `**` glob pattern instead of `/` in the
  "worktree without repository" tests, since `/` as a path pattern is
  Unix-specific and does not match Windows paths.
  Github CI pass: https://github.com/black-desk/git/actions/runs/26380466288
- Add a test verifying case-sensitive matching by default, with the
  `!CASE_INSENSITIVE_FS` prerequisite (suggested by Patrick Steinhardt).
- Link to v4: https://lore.kernel.org/r/20260513-includeif-worktree-v4-0-f8e6212d1fba@black-desk.cn (local)

Changes in v4:
- Deduplicate the worktree pattern documentation by referencing the
  gitdir syntax instead of repeating the full pattern description
  (suggested by Patrick Steinhardt).
- Add documentation comparing includeIf "worktree:" with
  extensions.worktreeConfig, including a concrete use case example
  (suggested by Phillip Wood, Junio C Hamano).
- Add a test verifying that the worktree condition does not match
  during early config reading (suggested by Patrick Steinhardt).
- Add tests for the non-repository (nongit) scenario (suggested by
  Patrick Steinhardt).
- Add a test for the case-insensitive "worktree/i" variant
- Link to v3: https://lore.kernel.org/r/20260403-includeif-worktree-v3-0-109ce5782b03@black-desk.cn (local)

Changes in v3:
- Apply Junio's suggestion.
- Link to v2: https://lore.kernel.org/r/20260402-includeif-worktree-v2-0-36e339b898d7@black-desk.cn (local)

Changes in v2:

- Add missing signed-off-by lines.
- Link to v1: https://lore.kernel.org/r/20260401-includeif-worktree-v1-0-906db69f2c79@black-desk.cn (local)

---
Chen Linxuan (2):
      config: refactor include_by_gitdir() into include_by_path()
      config: add "worktree" and "worktree/i" includeIf conditions

 Documentation/config.adoc |  48 +++++++++++++++++
 config.c                  |  25 +++++----
 t/t1305-config-include.sh | 128 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 190 insertions(+), 11 deletions(-)
---
base-commit: e9019fcafe0040228b8631c30f97ae1adb61bcdc
change-id: 20260401-includeif-worktree-fcb64950dfba

Best regards,
-- 
Chen Linxuan [off-list ref]