utils/git: Add linkify script.

llvm/utils/git/linkify

@@ -0,0 +1,20 @@
+#!/bin/sh
+
+# This script linkifies (i.e. makes clickable in the terminal) text that appears
+# to be a pull request or issue reference (e.g. #12345 or PR12345) or a
+# 40-character commit hash (e.g. abc123). You can configure git to automatically
+# send the output of commands that pipe their output through a pager, such as
+# `git log` and `git show`, through this script by running this command from
+# within your LLVM checkout:
+#
+# git config core.pager 'llvm/utils/git/linkify | pager'
+#
+# The pager command is run from the root of the repository even if the git
+# command is run from a subdirectory, so the relative path should always work.
+#
+# It requires OSC 8 support in the terminal. For a list of compatible terminals,
+# see https://github.com/Alhadis/OSC8-Adoption
+
+sed \
+  -e 's,\(#\|\bPR\)\([0-9]\+\),\x1b]8;;https://github.com/llvm/llvm-project/issues/\2\x1b\\\0\x1b]8;;\x1b\\,gi' \
+  -e 's,[0-9a-f]\{40\},\x1b]8;;https://github.com/llvm/llvm-project/commit/\0\x1b\\\0\x1b]8;;\x1b\\,g'