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

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

third_party/git/ci/lib.sh

@@ -34,6 +34,11 @@ save_good_tree () {
 # successfully before (e.g. because the branch got rebased, changing only
 # the commit messages).
 skip_good_tree () {
+	if test "$TRAVIS_DEBUG_MODE" = true || test true = "$GITHUB_ACTIONS"
+	then
+		return
+	fi
+
 	if ! good_tree_info="$(grep "^$(git rev-parse $CI_COMMIT^{tree}) " "$good_trees_file")"
 	then
 		# Haven't seen this tree yet, or no cached good trees file yet.
@@ -74,6 +79,9 @@ check_unignored_build_artifacts ()
 	}
 }
 
+# GitHub Action doesn't set TERM, which is required by tput
+export TERM=${TERM:-dumb}
+
 # Clear MAKEFLAGS that may come from the outside world.
 export MAKEFLAGS=
 
@@ -126,14 +134,33 @@ then
 		echo "$SYSTEM_TASKDEFINITIONSURI$SYSTEM_TEAMPROJECT/_build/results?buildId=$1"
 	}
 
-	BREW_INSTALL_PACKAGES=gcc@8
 	export GIT_PROVE_OPTS="--timer --jobs 10 --state=failed,slow,save"
 	export GIT_TEST_OPTS="--verbose-log -x --write-junit-xml"
 	MAKEFLAGS="$MAKEFLAGS --jobs=10"
 	test windows_nt != "$CI_OS_NAME" ||
 	GIT_TEST_OPTS="--no-chain-lint --no-bin-wrappers $GIT_TEST_OPTS"
+elif test true = "$GITHUB_ACTIONS"
+then
+	CI_TYPE=github-actions
+	CI_BRANCH="$GITHUB_REF"
+	CI_COMMIT="$GITHUB_SHA"
+	CI_OS_NAME="$(echo "$RUNNER_OS" | tr A-Z a-z)"
+	test macos != "$CI_OS_NAME" || CI_OS_NAME=osx
+	CI_REPO_SLUG="$GITHUB_REPOSITORY"
+	CI_JOB_ID="$GITHUB_RUN_ID"
+	CC="${CC:-gcc}"
+	DONT_SKIP_TAGS=t
+
+	cache_dir="$HOME/none"
+
+	export GIT_PROVE_OPTS="--timer --jobs 10"
+	export GIT_TEST_OPTS="--verbose-log -x"
+	MAKEFLAGS="$MAKEFLAGS --jobs=10"
+	test windows != "$CI_OS_NAME" ||
+	GIT_TEST_OPTS="--no-chain-lint --no-bin-wrappers $GIT_TEST_OPTS"
 else
 	echo "Could not identify CI type" >&2
+	env >&2
 	exit 1
 fi
 
@@ -141,6 +168,7 @@ good_trees_file="$cache_dir/good-trees"
 
 mkdir -p "$cache_dir"
 
+test -n "${DONT_SKIP_TAGS-}" ||
 skip_branch_tip_with_tag
 skip_good_tree
 
@@ -151,16 +179,20 @@ fi
 
 export DEVELOPER=1
 export DEFAULT_TEST_TARGET=prove
-export GIT_TEST_CLONE_2GB=YesPlease
+export GIT_TEST_CLONE_2GB=true
+export SKIP_DASHED_BUILT_INS=YesPlease
 
 case "$jobname" in
 linux-clang|linux-gcc)
 	if [ "$jobname" = linux-gcc ]
 	then
 		export CC=gcc-8
+		MAKEFLAGS="$MAKEFLAGS PYTHON_PATH=/usr/bin/python3"
+	else
+		MAKEFLAGS="$MAKEFLAGS PYTHON_PATH=/usr/bin/python2"
 	fi
 
-	export GIT_TEST_HTTPD=YesPlease
+	export GIT_TEST_HTTPD=true
 
 	# The Linux build installs the defined dependency versions below.
 	# The OS X build installs much more recent versions, whichever
@@ -177,7 +209,10 @@ linux-clang|linux-gcc)
 osx-clang|osx-gcc)
 	if [ "$jobname" = osx-gcc ]
 	then
-		export CC=gcc-8
+		export CC=gcc-9
+		MAKEFLAGS="$MAKEFLAGS PYTHON_PATH=$(which python3)"
+	else
+		MAKEFLAGS="$MAKEFLAGS PYTHON_PATH=$(which python2)"
 	fi
 
 	# t9810 occasionally fails on Travis CI OS X
@@ -185,9 +220,17 @@ osx-clang|osx-gcc)
 	# Travis CI OS X
 	export GIT_SKIP_TESTS="t9810 t9816"
 	;;
-GIT_TEST_GETTEXT_POISON)
+GETTEXT_POISON)
 	export GIT_TEST_GETTEXT_POISON=true
 	;;
+Linux32)
+	CC=gcc
+	;;
+linux-musl)
+	CC=gcc
+	MAKEFLAGS="$MAKEFLAGS PYTHON_PATH=/usr/bin/python3 USE_LIBPCRE2=Yes"
+	MAKEFLAGS="$MAKEFLAGS NO_REGEX=Yes ICONV_OMITS_BOM=Yes"
+	;;
 esac
 
 MAKEFLAGS="$MAKEFLAGS CC=${CC:-cc}"