merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 27 insertions, 0 deletions

diff --git a/third_party/git/ci/config/allow-ref.sample b/third_party/git/ci/config/allow-ref.sample
new file mode 100755
index 000000000000..af0e076f8a32
--- /dev/null
+++ b/third_party/git/ci/config/allow-ref.sample
@@ -0,0 +1,27 @@
+#!/bin/sh
+#
+# Sample script for enabling/disabling GitHub Actions CI runs on
+# particular refs. By default, CI is run for all branches pushed to
+# GitHub. You can override this by dropping the ".sample" from the script,
+# editing it, committing, and pushing the result to the "ci-config" branch of
+# your repository:
+#
+#   git checkout -b ci-config
+#   cp allow-ref.sample allow-ref
+#   $EDITOR allow-ref
+#   git add allow-ref
+#   git commit -am "implement my ci preferences"
+#   git push
+#
+# This script will then be run when any refs are pushed to that repository. It
+# gets the fully qualified refname as the first argument, and should exit with
+# success only for refs for which you want to run CI.
+
+case "$1" in
+# allow one-off tests by pushing to "for-ci" or "for-ci/mybranch"
+refs/heads/for-ci*) true ;;
+# always build your integration branch
+refs/heads/my-integration-branch) true ;;
+# don't build any other branches or tags
+*) false ;;
+esac