[PATCH v4 3/3] t, doc: update tests, reference for "--force-if-includes"

[Srinidhi Kaushik <shrinidhi.kaushik@gmail.com>]

* t/t5533-push-cas.sh:
    Updates test cases for "compare-and-swap" when used along with
    "--force-if-includes" helps mitigate overwrites when remote
    ref are updated in the background.

* Documentation:
    Adds reference for the new option, configuration setting
    ("push.useForceIfIncludes") and advise messages.

Signed-off-by: Srinidhi Kaushik <shrinidhi.kaushik@gmail.com>
---
 Documentation/config/advice.txt |  9 ++++--
 Documentation/config/push.txt   |  5 ++++
 Documentation/git-push.txt      | 20 +++++++++++++
 t/t5533-push-cas.sh             | 53 +++++++++++++++++++++++++++++++++
 4 files changed, 84 insertions(+), 3 deletions(-)

diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index bdd37c3eaa..acbd0c09aa 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -10,9 +10,8 @@ advice.*::
 		that the check is disabled.
 	pushUpdateRejected::
 		Set this variable to 'false' if you want to disable
-		'pushNonFFCurrent',
-		'pushNonFFMatching', 'pushAlreadyExists',
-		'pushFetchFirst', and 'pushNeedsForce'
+		'pushNonFFCurrent', 'pushNonFFMatching', 'pushAlreadyExists',
+		'pushFetchFirst', 'pushNeedsForce', and 'pushRefNeedsUpdate'
 		simultaneously.
 	pushNonFFCurrent::
 		Advice shown when linkgit:git-push[1] fails due to a
@@ -41,6 +40,10 @@ advice.*::
 		we can still suggest that the user push to either
 		refs/heads/* or refs/tags/* based on the type of the
 		source object.
+	pushRefNeedsUpdate::
+		Shown when linkgit:git-push[1] rejects a forced update of
+		a branch when its remote-tracking ref has updates that we
+		do not have locally.
 	statusAheadBehind::
 		Shown when linkgit:git-status[1] computes the ahead/behind
 		counts for a local ref compared to its remote tracking ref,
diff --git a/Documentation/config/push.txt b/Documentation/config/push.txt
index f5e5b38c68..6e57a27608 100644
--- a/Documentation/config/push.txt
+++ b/Documentation/config/push.txt
@@ -114,3 +114,8 @@ push.recurseSubmodules::
 	specifying '--recurse-submodules=check|on-demand|no'.
 	If not set, 'no' is used by default, unless 'submodule.recurse' is
 	set (in which case a 'true' value means 'on-demand').
+
+push.useForceIfIncludes::
+	If set to "true", it is equivalent to specifying "--force-if-includes"
+	as an argument to linkgit:git-push[1]. Adding "--no-force-if-includes"
+	the time of push overrides this configuration setting.
diff --git a/Documentation/git-push.txt b/Documentation/git-push.txt
index 3b8053447e..dc1215a5ad 100644
--- a/Documentation/git-push.txt
+++ b/Documentation/git-push.txt
@@ -320,6 +320,13 @@ seen and are willing to overwrite, then rewrite history, and finally
 force push changes to `master` if the remote version is still at
 `base`, regardless of what your local `remotes/origin/master` has been
 updated to in the background.
++
+Alternatively, specifying "--force-if-includes" an an ancillary option along
+with "--force-with-lease[=<refname>]" (i.e., without saying what exact commit
+the ref on the remote side must be pointing at, or which refs on the remote
+side are being protected) at the time of "push" will verify if updates from the
+remote-tracking refs that may have been implicitly updated in the background
+are integrated locally before allowing a forced update.
 
 -f::
 --force::
@@ -341,6 +348,19 @@ one branch, use a `+` in front of the refspec to push (e.g `git push
 origin +master` to force a push to the `master` branch). See the
 `<refspec>...` section above for details.
 
+--[no-]force-if-includes::
+	Force an update only if the tip of the remote-tracking ref
+	has been integrated locally.
++
+This option verifies if the tip of the remote-tracking ref on which
+a local branch has based on (for a rewrite), is reachable from at
+least one of the "reflog" entries of the local branch about to be
+updated by force on the remote. The check ensures that any updates
+from the remote have been incorporated locally by rejecting a push
+if that is not the case.
++
+Specifying "--no-force-if-includes" disables this behavior.
+
 --repo=<repository>::
 	This option is equivalent to the <repository> argument. If both
 	are specified, the command-line argument takes precedence.
diff --git a/t/t5533-push-cas.sh b/t/t5533-push-cas.sh
index 0b0eb1d025..60dd7d2f1c 100755
--- a/t/t5533-push-cas.sh
+++ b/t/t5533-push-cas.sh
@@ -256,4 +256,57 @@ test_expect_success 'background updates of REMOTE can be mitigated with a non-up
 	)
 '
 
+test_expect_success 'background updates of REMOTE can be mitigated with "--force-if-includes"' '
+	rm -rf src dst &&
+	git init --bare src.bare &&
+	test_when_finished "rm -rf src.bare" &&
+	git clone --no-local src.bare dst &&
+	test_when_finished "rm -rf dst" &&
+	(
+		cd dst &&
+		test_commit G &&
+		git push origin master:master
+	) &&
+	git clone --no-local src.bare dst2 &&
+	test_when_finished "rm -rf dst2" &&
+	(
+		cd dst2 &&
+		test_commit H &&
+		git push
+	) &&
+	(
+		cd dst &&
+		test_commit I &&
+		git fetch origin &&
+		test_must_fail git push --force-with-lease --force-if-includes origin
+	)
+'
+
+test_expect_success 'background updates of REMOTE can be mitigated with "push.useForceIfIncludes"' '
+	rm -rf src dst &&
+	git init --bare src.bare &&
+	test_when_finished "rm -rf src.bare" &&
+	git clone --no-local src.bare dst &&
+	test_when_finished "rm -rf dst" &&
+	(
+		cd dst &&
+		test_commit G &&
+		git push origin master:master
+	) &&
+	git clone --no-local src.bare dst2 &&
+	test_when_finished "rm -rf dst2" &&
+	(
+		cd dst2 &&
+		test_commit H &&
+		git push
+	) &&
+	(
+		cd dst &&
+		test_commit I &&
+		git fetch origin &&
+		git config --local push.useForceIfIncludes "true" &&
+		test_must_fail git push --force-if-includes origin
+	)
+'
+
 test_done
-- 
2.28.0