[PATCH v2 0/4] Add helpful advice about init.defaultBranch

It is our designated intention [https://sfconservancy.org/news/2020/jun/23/gitbranchname/] to "to explore changing the name of the first branch created automatically for new repositories away from ‘master’". Further, we promised that we "will minimize disruption for Git's users and will include appropriate deprecation periods".

To that end, we first clarify git init's documentation (a lightly edited version of Junio's patch [https://lore.kernel.org/git/xmqqd00a36wc.fsf@gitster.c.googlers.com]), and then introduce a message giving advice to users running git init that the fall-back for init.defaultBranch is subject to change, and how to override Git's fall-back manually.

The beauty of this patch series, if I may say so, is that it does not commit us to any concrete plan, but opens the door for all options regarding the default branch name.

Changes since v1:

 * Grammar fix
 * Reworded advice and commit messages
 * test_create_repo already respected GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME,
   but now does so more obviously
 * Allowed git branch -m <name> to rename unborn branches, so that the
   advice actually works

Johannes Schindelin (4):
  init: document `init.defaultBranch` better
  branch -m: allow renaming a yet-unborn branch
  get_default_branch_name(): prepare for showing some advice
  init: provide useful advice about init.defaultBranch

 Documentation/git-init.txt | 11 +++++++----
 builtin/branch.c           |  3 ++-
 builtin/clone.c            |  2 +-
 builtin/init-db.c          |  8 +++++---
 refs.c                     | 25 +++++++++++++++++++++----
 refs.h                     |  4 ++--
 remote.c                   |  5 +++--
 t/t0001-init.sh            | 15 ++++++++++++++-
 t/t1510-repo-setup.sh      |  2 +-
 t/test-lib-functions.sh    |  3 ++-
 10 files changed, 58 insertions(+), 20 deletions(-)

base-commit: faefdd61ec7c7f6f3c8c9907891465ac9a2a1475
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-921%2Fdscho%2Finit.defaultBranch-advice-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-921/dscho/init.defaultBranch-advice-v2
Pull-Request: https://github.com/git/git/pull/921

Range-diff vs v1:

 1:  1518387eaa ! 1:  483e490349 init: document `init.defaultBranch` better
     @@ Documentation/git-init.txt: If this is reinitialization, the repository will be
      -If not specified, fall back to the default name: `master`.
      +Use the specified name for the initial branch in the newly created
      +repository.  If not specified, fall back to the default name (currently
     -+`master`, but that will be changed in the future; The name can be customized
     ++`master`, but that will be changed in the future; the name can be customized
      +via the `init.defaultBranch` configuration variable).
       
       --shared[=(false|true|umask|group|all|world|everybody|0xxx)]::
 -:  ---------- > 2:  8de0c0eb22 branch -m: allow renaming a yet-unborn branch
 2:  42f6940043 = 3:  03314f7ac6 get_default_branch_name(): prepare for showing some advice
 3:  253d6706e6 ! 4:  bccef95391 init: provide useful advice about init.defaultBranch
     @@ Metadata
       ## Commit message ##
          init: provide useful advice about init.defaultBranch
      
     -    To give ample warning in case we decide to change the fall-back for an
     -    unconfigured `init.defaultBranch`, let's introduce some advice that is
     -    shown upon `git init` when that value is not set.
     +    To give ample warning for users wishing to override Git's the fall-back
     +    for an unconfigured `init.defaultBranch` (in case we decide to change it
     +    in a future Git version), let's introduce some advice that is shown upon
     +    `git init` when that value is not set.
      
     -    Note: three test cases in Git's test suite want to verify that the
     +    Note: two test cases in Git's test suite want to verify that the
          `stderr` output of `git init` is empty. With this patch, that is only
          true if `init.defaultBranch` is configured, so let's do exactly that in
          those test cases. The same reasoning applies to `test_create_repo()`.
     @@ refs.c: void expand_ref_prefix(struct strvec *prefixes, const char *prefix)
       }
       
      +static const char default_branch_name_advice[] = N_(
     -+"Using '%s' as the name for the initial branch. This name is subject\n"
     -+"to change. To configure the name to use as the initial branch name in\n"
     -+"new repositories, or to silence this warning, run:\n"
     ++"Using '%s' as the name for the initial branch. This default branch name\n"
     ++"is subject to change. To configure the initial branch name to use in all\n"
     ++"of your new repositories, run:\n"
      +"\n"
      +"\tgit config --global init.defaultBranch <name>\n"
     ++"\n"
     ++"Common names are 'main', 'trunk' and 'development'. If you merely wish\n"
     ++"to suppress this warning, you can also use the current default branch\n"
     ++"name. The current branch can be renamed via this command:\n"
     ++"\n"
     ++"\tgit branch -m <name>\n"
      +);
      +
       char *repo_default_branch_name(struct repository *r, int quiet)
     @@ t/t1510-repo-setup.sh: setup_repo () {
       	maybe_config "$name/.git/config" core.bare "$barecfg" &&
       	mkdir -p "$name/sub/sub" &&
      
     - ## t/t7414-submodule-mistakes.sh ##
     -@@ t/t7414-submodule-mistakes.sh: test_expect_success 'no warning when updating entry' '
     - 
     - test_expect_success 'submodule add does not warn' '
     - 	test_when_finished "git rm -rf submodule .gitmodules" &&
     --	git submodule add ./embed submodule 2>stderr &&
     -+	git -c init.defaultBranch=x submodule add ./embed submodule 2>stderr &&
     - 	test_i18ngrep ! warning stderr
     - '
     - 
     -
       ## t/test-lib-functions.sh ##
      @@ t/test-lib-functions.sh: test_create_repo () {
       	mkdir -p "$repo"
     @@ t/test-lib-functions.sh: test_create_repo () {
       		cd "$repo" || error "Cannot setup test environment"
      -		"${GIT_TEST_INSTALLED:-$GIT_EXEC_PATH}/git$X" init \
      +		"${GIT_TEST_INSTALLED:-$GIT_EXEC_PATH}/git$X" \
     -+			-c init.defaultBranch=master init \
     ++			-c init.defaultBranch=${GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME-master} init \
       			"--template=$GIT_BUILD_DIR/templates/blt/" >&3 2>&4 ||
       		error "cannot run git init -- have you built things yet?"
       		mv .git/hooks .git/hooks-disabled