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[PATCH v2 1/2] merge: new autosetupmerge option 'simple' for matching branches

From
Tao Klerks via GitGitGadget <gitgitgadget@gmail.com>
Date
Feb 25, 2022, 18:52 UTC
Message-ID
<890e016bfc0809d25a4ae8ae924b23895f520810.1645815142.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.1161.v2.git.1645815142.gitgitgadget@gmail.com>
From: Tao Klerks <tao@klerks.biz>

This commit introduces a new option to the branch.autosetupmerge setting, "simple", which is intended to be consistent with and complementary to the push.default "simple" option.

The push.defaut option "simple" helps produce predictable/understandable behavior for beginners, where they don't accidentally push to the "wrong" branch in centralized workflows. If they create a local branch with a different name and then try to do a plain push, it will helpfully fail and explain why.

However, such users can often find themselves confused by the behavior of git after they first branch, and before they push. At that stage, their upstream tracking branch is the original remote branch, and pull will be bringing in "upstream changes" - eg all changes to "main", in a typical project where that's where they branched from. On the other hand, once they push their new branch (dealing with the initial error, following instructions to push to the right name), subsequent "pull" calls will behave as expected, only bring in any changes to that new branch they pushed.

The new option introduced here, with push.default set to simple, ensures that push/pull behavior is generally consistent - tracking will be automatically set up for branches that push will work for (and pull will be consistent for) only.

Signed-off-by: Tao Klerks <tao@klerks.biz>
---
 Documentation/config/branch.txt |  4 +++-
 Documentation/git-branch.txt    | 18 +++++++++++-------
 branch.c                        | 19 +++++++++++++++++++
 branch.h                        |  1 +
 config.c                        |  3 +++
 5 files changed, 37 insertions(+), 8 deletions(-)
diff --git a/Documentation/config/branch.txt b/Documentation/config/branch.txt
index 1e0c7af014b..8df10d07129 100644
--- a/Documentation/config/branch.txt
+++ b/Documentation/config/branch.txt
@@ -9,7 +9,9 @@ branch.autoSetupMerge::
 	automatic setup is done when the starting point is either a
 	local branch or remote-tracking branch; `inherit` -- if the starting point
 	has a tracking configuration, it is copied to the new
-	branch. This option defaults to true.
+	branch; `simple` -- automatic setup is done only when the starting point
+	is a remote-tracking branch and the new branch has the same name as the
+	remote branch. This option defaults to true.
 
 branch.autoSetupRebase::
 	When a new branch is created with 'git branch', 'git switch' or 'git checkout'
diff --git a/Documentation/git-branch.txt b/Documentation/git-branch.txt
index c8b4f9ce3c7..ae82378349d 100644
--- a/Documentation/git-branch.txt
+++ b/Documentation/git-branch.txt
@@ -221,13 +221,17 @@ The exact upstream branch is chosen depending on the optional argument:
 itself as the upstream; `--track=inherit` means to copy the upstream
 configuration of the start-point branch.
 +
-`--track=direct` is the default when the start point is a remote-tracking branch.
-Set the branch.autoSetupMerge configuration variable to `false` if you
-want `git switch`, `git checkout` and `git branch` to always behave as if `--no-track`
-were given. Set it to `always` if you want this behavior when the
-start-point is either a local or remote-tracking branch. Set it to
-`inherit` if you want to copy the tracking configuration from the
-branch point.
+The branch.autoSetupMerge configuration variable specifies how `git switch`,
+`git checkout` and `git branch` should behave when neither `--track` nor
+`--no-track` are specified:
++
+The default option, `true`, behaves as though `--track=direct`
+were given whenever the start-point is a remote-tracking branch.
+`false` behaves as if `--no-track` were given. `always` behaves as though
+`--track=direct` were given. `inherit` behaves as though `--track=inherit`
+were given. `simple` behaves as though `--track=direct` were given only when
+the start-point is a remote-tracking branch and the new branch has the same
+name as the remote branch.
 +
 See linkgit:git-pull[1] and linkgit:git-config[1] for additional discussion on
 how the `branch.<name>.remote` and `branch.<name>.merge` options are used.
diff --git a/branch.c b/branch.c
index 6b31df539a5..81613ade8bf 100644
--- a/branch.c
+++ b/branch.c
@@ -252,10 +252,29 @@ static void setup_tracking(const char *new_ref, const char *orig_ref,
 			goto cleanup;
 		}
 
+	/*
+	 * This check does not apply to the BRANCH_TRACK_INHERIT
+	 * option; you can inherit one or more tracking entries
+	 * and the tracking.matches counter is not incremented.
+	 */
 	if (tracking.matches > 1)
 		die(_("not tracking: ambiguous information for ref %s"),
 		    orig_ref);
 
+	if (track == BRANCH_TRACK_SIMPLE) {
+		/*
+		 * Only track if remote branch name matches.
+		 * Reaching into items[0].string is safe because
+		 * we know there is at least one and not more than
+		 * one entry (because not BRANCH_TRACK_INHERIT).
+		 */
+		const char *tracked_branch;
+		if (!skip_prefix(tracking.srcs->items[0].string,
+				 "refs/heads/", &tracked_branch) ||
+		    strcmp(tracked_branch, new_ref))
+			return;
+	}
+
 	if (tracking.srcs->nr < 1)
 		string_list_append(tracking.srcs, orig_ref);
 	if (install_branch_config_multiple_remotes(config_flags, new_ref,
diff --git a/branch.h b/branch.h
index 04df2aa5b51..560b6b96a8f 100644
--- a/branch.h
+++ b/branch.h
@@ -12,6 +12,7 @@ enum branch_track {
 	BRANCH_TRACK_EXPLICIT,
 	BRANCH_TRACK_OVERRIDE,
 	BRANCH_TRACK_INHERIT,
+	BRANCH_TRACK_SIMPLE,
 };
 
 extern enum branch_track git_branch_track;
diff --git a/config.c b/config.c
index e0c03d154c9..cc586ac816c 100644
--- a/config.c
+++ b/config.c
@@ -1673,6 +1673,9 @@ static int git_default_branch_config(const char *var, const char *value)
 		} else if (value && !strcmp(value, "inherit")) {
 			git_branch_track = BRANCH_TRACK_INHERIT;
 			return 0;
+		} else if (value && !strcmp(value, "simple")) {
+			git_branch_track = BRANCH_TRACK_SIMPLE;
+			return 0;
 		}
 		git_branch_track = git_config_bool(var, value);
 		return 0;
-- 
gitgitgadget
Previous: Tao Klerks via GitGitGadgetNext: Junio C Hamano
Message 8 of 41 in “adding new branch.autosetupmerge option "simple"”
  1. 0/3 adding new branch.autosetupmerge option "simple"Tao Klerks via GitGitGadget, Feb 24, 2022
  2. 1/3 merge: new autosetupmerge option 'simple' for matching branchesTao Klerks via GitGitGadget, Feb 24, 2022
  3. Junio C HamanoFeb 24, 2022
  4. 2/3 t3200: tests for new branch.autosetupmerge option "simple"Tao Klerks via GitGitGadget, Feb 24, 2022
  5. 3/3 branch documentation: new autosetupmerge option "simple"Tao Klerks via GitGitGadget, Feb 24, 2022
  6. Junio C HamanoFeb 24, 2022
  7. 0/2 adding new branch.autosetupmerge option "simple"Tao Klerks via GitGitGadget, Feb 25, 2022
  8. 1/2 merge: new autosetupmerge option 'simple' for matching branchesTao Klerks via GitGitGadget, Feb 25, 2022
  9. Junio C HamanoFeb 25, 2022
  10. Tao KlerksFeb 27, 2022
  11. 2/2 t3200: tests for new branch.autosetupmerge option "simple"Tao Klerks via GitGitGadget, Feb 25, 2022
  12. 0/2 adding new branch.autosetupmerge option "simple"Tao Klerks via GitGitGadget, Feb 28, 2022
  13. 2/2 t3200: tests for new branch.autosetupmerge option "simple"Tao Klerks via GitGitGadget, Feb 28, 2022
  14. Ævar Arnfjörð BjarmasonFeb 28, 2022
  15. Eric SunshineMar 1, 2022
  16. Tao KlerksMar 1, 2022
  17. Tao KlerksMar 1, 2022
  18. 1/2 merge: new autosetupmerge option 'simple' for matching branchesTao Klerks via GitGitGadget, Feb 28, 2022
  19. Ævar Arnfjörð BjarmasonFeb 28, 2022
  20. Tao KlerksMar 2, 2022
  21. Tao KlerksMar 20, 2022
  22. merge: new autosetupmerge option 'simple' for matching branchesTao Klerks via GitGitGadget, Mar 21, 2022
  23. Josh SteadmonApr 18, 2022
  24. Tao KlerksApr 20, 2022
  25. Josh SteadmonApr 20, 2022
  26. Junio C HamanoApr 20, 2022
  27. Tao KlerksApr 20, 2022
  28. Junio C HamanoApr 21, 2022
  29. Tao KlerksApr 21, 2022
  30. Junio C HamanoApr 22, 2022
  31. Tao KlerksApr 22, 2022
  32. Tao KlerksApr 22, 2022
  33. Junio C HamanoApr 23, 2022
  34. Tao KlerksApr 24, 2022
  35. Tao KlerksApr 29, 2022
  36. 0/3 New options to support "simple" centralized workflowTao Klerks via GitGitGadget, Apr 29, 2022
  37. 1/3 branch: new autosetupmerge option 'simple' for matching branchesTao Klerks via GitGitGadget, Apr 29, 2022
  38. 2/3 push: default to single remote even when not named originTao Klerks via GitGitGadget, Apr 29, 2022
  39. 3/3 push: new config option "push.autoSetupRemote" supports "simple" pushTao Klerks via GitGitGadget, Apr 29, 2022
  40. Junio C HamanoApr 29, 2022
  41. Tao KlerksApr 30, 2022

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