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

Submitted-As: https://lore.kernel.org/git/pull.1577.v5.git.git.1697218770.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1577.git.git.1695218431033.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1577.v2.git.git.1696443502.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1577.v3.git.git.1696967380.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1577.v4.git.git.1697044422.gitgitgadget@gmail.com