merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/contrib/rerere-train.sh

@@ -0,0 +1,102 @@
+#!/bin/sh
+# Copyright (c) 2008, Nanako Shiraishi
+# Prime rerere database from existing merge commits
+
+me=rerere-train
+USAGE=$(cat <<-EOF
+usage: $me [--overwrite] <rev-list-args>
+
+    -h, --help            show the help
+    -o, --overwrite       overwrite any existing rerere cache
+EOF
+)
+
+SUBDIRECTORY_OK=Yes
+
+overwrite=0
+
+while test $# -gt 0
+do
+	opt="$1"
+	case "$opt" in
+	-h|--help)
+		echo "$USAGE"
+		exit 0
+		;;
+	-o|--overwrite)
+		overwrite=1
+		shift
+		break
+		;;
+	--)
+		shift
+		break
+		;;
+	*)
+		break
+		;;
+	esac
+done
+
+# Overwrite or help options are not valid except as first arg
+for opt in "$@"
+do
+	case "$opt" in
+	-h|--help)
+		echo "$USAGE"
+		exit 0
+		;;
+	-o|--overwrite)
+		echo "$USAGE"
+		exit 0
+		;;
+	esac
+done
+
+. "$(git --exec-path)/git-sh-setup"
+require_work_tree
+cd_to_toplevel
+
+# Remember original branch
+branch=$(git symbolic-ref -q HEAD) ||
+original_HEAD=$(git rev-parse --verify HEAD) || {
+	echo >&2 "Not on any branch and no commit yet?"
+	exit 1
+}
+
+mkdir -p "$GIT_DIR/rr-cache" || exit
+
+git rev-list --parents "$@" |
+while read commit parent1 other_parents
+do
+	if test -z "$other_parents"
+	then
+		# Skip non-merges
+		continue
+	fi
+	git checkout -q "$parent1^0"
+	if git merge $other_parents >/dev/null 2>&1
+	then
+		# Cleanly merges
+		continue
+	fi
+	if test $overwrite = 1
+	then
+		git rerere forget .
+	fi
+	if test -s "$GIT_DIR/MERGE_RR"
+	then
+		git show -s --pretty=format:"Learning from %h %s" "$commit"
+		git rerere
+		git checkout -q $commit -- .
+		git rerere
+	fi
+	git reset -q --hard
+done
+
+if test -z "$branch"
+then
+	git checkout "$original_HEAD"
+else
+	git checkout "${branch#refs/heads/}"
+fi