revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/ci/install-dependencies.sh

@@ -40,30 +40,20 @@ osx-clang|osx-gcc)
 	test -z "$BREW_INSTALL_PACKAGES" ||
 	brew install $BREW_INSTALL_PACKAGES
 	brew link --force gettext
-	brew cask install --no-quarantine perforce || {
-		# Update the definitions and try again
-		cask_repo="$(brew --repository)"/Library/Taps/homebrew/homebrew-cask &&
-		git -C "$cask_repo" pull --no-stat &&
-		brew cask install --no-quarantine perforce
-	} ||
 	brew install caskroom/cask/perforce
 	case "$jobname" in
 	osx-gcc)
-		brew install gcc@9
-		# Just in case the image is updated to contain gcc@9
-		# pre-installed but not linked.
-		brew link gcc@9
+		brew link gcc@8
 		;;
 	esac
 	;;
 StaticAnalysis)
 	sudo apt-get -q update
-	sudo apt-get -q -y install coccinelle libcurl4-openssl-dev libssl-dev \
-		libexpat-dev gettext
+	sudo apt-get -q -y install coccinelle
 	;;
 Documentation)
 	sudo apt-get -q update
-	sudo apt-get -q -y install asciidoc xmlto docbook-xsl-ns
+	sudo apt-get -q -y install asciidoc xmlto
 
 	test -n "$ALREADY_HAVE_ASCIIDOCTOR" ||
 	gem install --version 1.5.8 asciidoctor

third_party/git/ci/lib.sh

@@ -34,11 +34,6 @@ save_good_tree () {
 # successfully before (e.g. because the branch got rebased, changing only
 # the commit messages).
 skip_good_tree () {
-	if test "$TRAVIS_DEBUG_MODE" = true
-	then
-		return
-	fi
-
 	if ! good_tree_info="$(grep "^$(git rev-parse $CI_COMMIT^{tree}) " "$good_trees_file")"
 	then
 		# Haven't seen this tree yet, or no cached good trees file yet.
@@ -131,6 +126,7 @@ 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"
@@ -155,7 +151,7 @@ fi
 
 export DEVELOPER=1
 export DEFAULT_TEST_TARGET=prove
-export GIT_TEST_CLONE_2GB=true
+export GIT_TEST_CLONE_2GB=YesPlease
 
 case "$jobname" in
 linux-clang|linux-gcc)
@@ -164,7 +160,7 @@ linux-clang|linux-gcc)
 		export CC=gcc-8
 	fi
 
-	export GIT_TEST_HTTPD=true
+	export GIT_TEST_HTTPD=YesPlease
 
 	# The Linux build installs the defined dependency versions below.
 	# The OS X build installs much more recent versions, whichever
@@ -181,7 +177,7 @@ linux-clang|linux-gcc)
 osx-clang|osx-gcc)
 	if [ "$jobname" = osx-gcc ]
 	then
-		export CC=gcc-9
+		export CC=gcc-8
 	fi
 
 	# t9810 occasionally fails on Travis CI OS X

third_party/git/ci/run-build-and-tests.sh

@@ -20,7 +20,6 @@ linux-gcc)
 	export GIT_TEST_OE_DELTA_SIZE=5
 	export GIT_TEST_COMMIT_GRAPH=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
-	export GIT_TEST_ADD_I_USE_BUILTIN=1
 	make test
 	;;
 linux-gcc-4.8)

third_party/git/ci/run-static-analysis.sh

@@ -26,7 +26,4 @@ then
 	exit 1
 fi
 
-make hdr-check ||
-exit 1
-
 save_good_tree

third_party/git/ci/test-documentation.sh

@@ -7,10 +7,7 @@
 
 filter_log () {
 	sed -e '/^GIT_VERSION = /d' \
-	    -e "/constant Gem::ConfigMap is deprecated/d" \
 	    -e '/^    \* new asciidoc flags$/d' \
-	    -e '/stripped namespace before processing/d' \
-	    -e '/Attributed.*IDs for element/d' \
 	    "$1"
 }