[PATCH v4 0/4] Add helpful advice about init.defaultBranch

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

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 v3:

 * Kicked out advice.defaultBranchName again. The advice can now only be
   suppressed by setting init.defaultBranch.

Changes since v2:

 * git branch -m <initial> <renamed> now works, too
 * The config setting advice.defaultBranchName was introduced to allow
   suppressing this warning specifically
 * The advice now first talks about the current default branch name, then
   how to suppress the advice, and only then explains how to override the
   default branch name (and that that will also prevent the message from
   being shown)

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           |  4 +++-
 builtin/clone.c            |  2 +-
 builtin/init-db.c          |  8 +++++---
 refs.c                     | 24 ++++++++++++++++++++----
 refs.h                     |  4 ++--
 remote.c                   |  5 +++--
 t/t0001-init.sh            | 17 ++++++++++++++++-
 t/t1510-repo-setup.sh      |  2 +-
 t/test-lib-functions.sh    |  4 +++-
 10 files changed, 61 insertions(+), 20 deletions(-)


base-commit: faefdd61ec7c7f6f3c8c9907891465ac9a2a1475
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-921%2Fdscho%2Finit.defaultBranch-advice-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-921/dscho/init.defaultBranch-advice-v4
Pull-Request: https://github.com/git/git/pull/921

Range-diff vs v3:

 1:  483e4903491 = 1:  483e4903491 init: document `init.defaultBranch` better
 2:  6cbd6692c6a = 2:  6cbd6692c6a branch -m: allow renaming a yet-unborn branch
 3:  5fc15f7b9ad = 3:  5fc15f7b9ad get_default_branch_name(): prepare for showing some advice
 4:  87c93068771 ! 4:  2f21c505d56 init: provide useful advice about init.defaultBranch
     @@ Commit message
      
          Note: two test cases in Git's test suite want to verify that the
          `stderr` output of `git init` is empty. It is now necessary to suppress
     -    the advice using the newly-added `advice.defaultBranchName` setting.
     -    While not strictly necessary, we also set this to `false` in
     +    the advice, we now do that via the `init.defaultBranch` setting. While
     +    not strictly necessary, we also set this to `false` in
          `test_create_repo()`.
      
          Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
      
     - ## advice.c ##
     -@@ advice.c: static struct {
     - 	[ADVICE_AM_WORK_DIR] 				= { "amWorkDir", 1 },
     - 	[ADVICE_CHECKOUT_AMBIGUOUS_REMOTE_BRANCH_NAME] 	= { "checkoutAmbiguousRemoteBranchName", 1 },
     - 	[ADVICE_COMMIT_BEFORE_MERGE]			= { "commitBeforeMerge", 1 },
     -+	[ADVICE_DEFAULT_BRANCH_NAME]			= { "defaultBranchName", 1 },
     - 	[ADVICE_DETACHED_HEAD]				= { "detachedHead", 1 },
     - 	[ADVICE_FETCH_SHOW_FORCED_UPDATES]		= { "fetchShowForcedUpdates", 1 },
     - 	[ADVICE_GRAFT_FILE_DEPRECATED]			= { "graftFileDeprecated", 1 },
     -
     - ## advice.h ##
     -@@ advice.h: extern int advice_add_empty_pathspec;
     - 	ADVICE_AM_WORK_DIR,
     - 	ADVICE_CHECKOUT_AMBIGUOUS_REMOTE_BRANCH_NAME,
     - 	ADVICE_COMMIT_BEFORE_MERGE,
     -+	ADVICE_DEFAULT_BRANCH_NAME,
     - 	ADVICE_DETACHED_HEAD,
     - 	ADVICE_FETCH_SHOW_FORCED_UPDATES,
     - 	ADVICE_GRAFT_FILE_DEPRECATED,
     -
       ## refs.c ##
     -@@
     - #include "strvec.h"
     - #include "repository.h"
     - #include "sigchain.h"
     -+#include "advice.h"
     - 
     - /*
     -  * List of all available backends
      @@ refs.c: void expand_ref_prefix(struct strvec *prefixes, const char *prefix)
       		strvec_pushf(prefixes, *p, len, prefix);
       }
       
      +static const char default_branch_name_advice[] = N_(
      +"Using '%s' as the name for the initial branch. This default branch name\n"
     -+"is subject to change. To suppress this warning, run:\n"
     -+"\n"
     -+"\tgit config --global advice.defaultBranchName false\n"
     -+"\n"
     -+"Alternatively, you can configure the initial branch name to use in all\n"
     -+"of your new repositories, which will also suppress this warning:\n"
     ++"is subject to change. To configure the initial branch name to use in all\n"
     ++"of your new repositories, which will suppress this warning, call:\n"
      +"\n"
      +"\tgit config --global init.defaultBranch <name>\n"
      +"\n"
     @@ refs.c: char *repo_default_branch_name(struct repository *r, int quiet)
      -	if (!ret)
      +	if (!ret) {
       		ret = xstrdup("master");
     -+		if (!quiet && advice_enabled(ADVICE_DEFAULT_BRANCH_NAME))
     ++		if (!quiet)
      +			advise(_(default_branch_name_advice), ret);
      +	}
       
     @@ t/t0001-init.sh: test_expect_success 'reinit' '
       		mkdir again &&
       		cd again &&
      -		git init >out1 2>err1 &&
     -+		git -c advice.defaultBranchName=false init >out1 2>err1 &&
     ++		git -c init.defaultBranch=initial init >out1 2>err1 &&
       		git init >out2 2>err2
       	) &&
       	test_i18ngrep "Initialized empty" again/out1 &&
     @@ t/t1510-repo-setup.sh: setup_repo () {
       	sane_unset GIT_DIR GIT_WORK_TREE &&
       
      -	git init "$name" &&
     -+	git -c advice.defaultBranchName=false init "$name" &&
     ++	git -c init.defaultBranch=initial init "$name" &&
       	maybe_config "$name/.git/config" core.worktree "$worktreecfg" &&
       	maybe_config "$name/.git/config" core.bare "$barecfg" &&
       	mkdir -p "$name/sub/sub" &&
     @@ 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$X" \
     -+			-c advice.defaultBranchName=false init \
     ++		"${GIT_TEST_INSTALLED:-$GIT_EXEC_PATH}/git$X" -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

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