branch: add flags and config to inherit tracking

It can be helpful when creating a new branch to use the existing
tracking configuration from the branch point. However, there is
currently not a method to automatically do so.

Teach git-{branch,checkout,switch} an "inherit" argument to the
"--track" option. When this is set, creating a new branch will cause the
tracking configuration to default to the configuration of the branch
point, if set.

For example, if branch "main" tracks "origin/main", and we run
`git checkout --track=inherit -b feature main`, then branch "feature"
will track "origin/main". Thus, `git status` will show us how far
ahead/behind we are from origin, and `git pull` will pull from origin.

This is particularly useful when creating branches across many
submodules, such as with `git submodule foreach ...` (or if running with
a patch such as [1], which we use at $job), as it avoids having to
manually set tracking info for each submodule.

Since we've added an argument to "--track", also add "--track=direct" as
another way to explicitly get the original "--track" behavior ("--track"
without an argument still works as well).

Finally, teach branch.autoSetupMerge a new "inherit" option. When this
is set, "--track=inherit" becomes the default behavior.

[1]: https://lore.kernel.org/git/20180927221603.148025-1-sbeller@google.com/

Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/t/t2060-switch.sh b/t/t2060-switch.sh
index 9bc6a3aa5c..ebb961be29 100755
--- a/t/t2060-switch.sh
+++ b/t/t2060-switch.sh
@@ -107,4 +107,32 @@ test_expect_success 'not switching when something is in progress' '
 	test_must_fail git switch -d @^
 '
 
+test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
+	# default config does not copy tracking info
+	git switch -c foo-no-inherit foo &&
+	test_cmp_config "" --default "" branch.foo-no-inherit.remote &&
+	test_cmp_config "" --default "" branch.foo-no-inherit.merge &&
+	# with --track=inherit, we copy tracking info from foo
+	git switch --track=inherit -c foo2 foo &&
+	test_cmp_config origin branch.foo2.remote &&
+	test_cmp_config refs/heads/foo branch.foo2.merge &&
+	# with autoSetupMerge=inherit, we do the same
+	test_config branch.autoSetupMerge inherit &&
+	git switch -c foo3 foo &&
+	test_cmp_config origin branch.foo3.remote &&
+	test_cmp_config refs/heads/foo branch.foo3.merge &&
+	# with --track, we override autoSetupMerge
+	git switch --track -c foo4 foo &&
+	test_cmp_config . branch.foo4.remote &&
+	test_cmp_config refs/heads/foo branch.foo4.merge &&
+	# and --track=direct does as well
+	git switch --track=direct -c foo5 foo &&
+	test_cmp_config . branch.foo5.remote &&
+	test_cmp_config refs/heads/foo branch.foo5.merge &&
+	# no tracking info to inherit from main
+	git switch -c main2 main &&
+	test_cmp_config "" --default "" branch.main2.remote &&
+	test_cmp_config "" --default "" branch.main2.merge
+'
+
 test_done