[PATCH v5 0/2] attr: add attr.tree config

44451a2e5e (attr: teach "--attr-source=" global option to "git", 2023-05-06) provided the ability to pass in a treeish as the attr source. When a revision does not resolve to a valid tree is passed, Git will die. At GitLab, we server repositories as bare repos and would like to always read attributes from the default branch, so we'd like to pass in HEAD as the treeish to read gitattributes from on every command. In this context we would not want Git to die if HEAD is unborn, like in the case of empty repositories.

Instead of modifying the default behavior of --attr-source, create a new config attr.tree with which an admin can configure a ref for all commands to read gitattributes from. Also make the default tree to read from HEAD on bare repositories.

Changes since v4:

 * removed superfluous test

Changes since v3:

 * clarified attr logic around ignoring errors if source set by attr.tree is
   invalid
 * refactored tests by using helpers
 * modified test to check for precedence between --attr-source, attr.tree,
   GIT_ATTR_SOURCE

Changes since v2:

 * relax the restrictions around attr.tree so that if it does not resolve to
   a valid treeish, ignore it.
 * add a commit to default to HEAD in bare repositories
 * remove commit that adds attr.allowInvalidSource

Changes since v1:

 * Added a commit to add attr.tree config

John Cai (2):
  attr: read attributes from HEAD when bare repo
  attr: add attr.tree for setting the treeish to read attributes from

 Documentation/config.txt      |  2 +
 Documentation/config/attr.txt |  7 ++++
 attr.c                        | 19 ++++++++-
 attr.h                        |  2 +
 config.c                      | 16 ++++++++
 t/t0003-attributes.sh         | 72 +++++++++++++++++++++++++++++++++++
 t/t5001-archive-attr.sh       |  2 +-
 7 files changed, 118 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/config/attr.txt

base-commit: 1fc548b2d6a3596f3e1c1f8b1930d8dbd1e30bf3
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1577%2Fjohn-cai%2Fjc%2Fconfig-attr-invalid-source-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1577/john-cai/jc/config-attr-invalid-source-v5
Pull-Request: https://github.com/git/git/pull/1577

Range-diff vs v4:

 1:  eaa27c47810 = 1:  eaa27c47810 attr: read attributes from HEAD when bare repo
 2:  749d8a8082e ! 2:  df4b3f53309 attr: add attr.tree for setting the treeish to read attributes from
     @@ t/t0003-attributes.sh: test_expect_success 'bare repository: check that .gitattr
      +	)
      +'
      +
     -+test_expect_success 'attr.tree points to non-existing ref' '
     -+	test_when_finished rm -rf empty &&
     -+	git init empty &&
     -+	(
     -+		cd empty &&
     -+		echo "f/path: test: unspecified" >expect &&
     -+		git -c attr.tree=refs/does/not/exist check-attr test -- f/path >actual 2>err &&
     -+		test_must_be_empty err &&
     -+		test_cmp expect actual
     -+	)
     -+'
     -+
      +test_expect_success 'bad attr source defaults to reading .gitattributes file' '
      +	test_when_finished rm -rf empty &&
      +	git init empty &&