gitiles script to generate/open gitiles URLs

We often use gitiles links to point to some source code which is
relevant for a discussion or code review. It often requires 10-15
mouse clicks in order to navigate to a path in gitiles and generate a
link. This is cumbersome and may discourage providing links to gitiles.

This script intends to provide a fast way to generate and open gitiles
links. It requires a one time setup of gitiles.url in .git/config file:

  [gitiles]
    url = https://gerrit.googlesource.com/gerrit

Once gitiles.url is setup we can generate gitiles URLs easily.

Examples
========

* print gitiles URL for the current HEAD and current directory:

  $ gitiles
  https://gerrit.googlesource.com/gerrit/+/d685ac1193e086b896cfc019ef4504d1b7ce455b/

* print gitiles URL for current HEAD and Documentation directory:

  $ gitiles Documentation

* print gitiles URL for branch stable-2.15 and current directory:

  $ gitiles -b stable-2.15

* print gitiles URL for current HEAD and a path relative to the current directory:

  $ pwd
  gerrit-server
  $ gitiles ./src/main/resources

The script also supports "open" command which open gitiles URL using
OS's native way of opening URLs:

  $ gitiles open
  $ gitiles open -b stable-2.15 Documentation

Change-Id: Icd31723711535e886313d3d17afb57caa4a710b1

contrib/gitiles

@@ -0,0 +1,84 @@
+#!/bin/bash
+#
+# Copyright (C) 2018 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+usage() {
+  me=`basename "$0"`
+  echo >&2 "Usage: $me [open] [-b branch] [path]"
+  exit 1
+}
+
+cmd_open() {
+  case "$(uname)" in
+    Darwin)
+      echo "open"
+      ;;
+    Linux)
+      echo "xdg-open"
+      ;;
+
+    *)
+      echo >&2 "Don't know how to open URLs on $(uname)"
+      exit 1
+  esac
+}
+
+URL=$(git config --get gitiles.url)
+
+if test -z "$URL" ; then
+  echo >&2 "gitiles.url must be set in .git/config"
+  exit 1
+fi
+
+while test $# -gt 0 ; do
+  case "$1" in
+  open)
+    CMD=$(cmd_open)
+    shift
+    ;;
+  -b|--branch)
+    shift
+    B=$1
+    shift
+    ;;
+  -h|--help)
+    usage
+    ;;
+
+  *)
+    P=$1
+    shift
+  esac
+done
+
+if test -z "$CMD" ; then
+  CMD=echo
+fi
+
+if test -z "$B" ; then
+  B=$(git rev-parse HEAD)
+fi
+
+URL="$URL/+/$B"
+
+if test -z "$P" ; then
+  P=$(git rev-parse --show-prefix)
+elif test ${P:0:2} = "./" ; then
+  P=$(git rev-parse --show-prefix)${P:2}
+fi
+
+URL="$URL/$P"
+
+$CMD $URL