doc: Add generate_git.sh, which updates the checked-in generated docs

BUG=crashpad:67
R=agable@chromium.org

Review URL: https://codereview.chromium.org/1399623002 .

doc/support/generate_git.sh

@@ -0,0 +1,85 @@
+#!/bin/bash
+
+# Copyright 2015 The Crashpad Authors. All rights reserved.
+#
+# 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.
+
+set -e
+
+# Run from the Crashpad project root directory.
+cd "$(dirname "${0}")/../.."
+
+source doc/support/compat.sh
+
+basename="$(basename "${0}")"
+
+status="$(git status --porcelain)"
+if [[ -n "${status}" ]]; then
+  echo "${basename}: the working directory must be clean" >& 2
+  git status
+  exit 1
+fi
+
+# git symbolic-ref gives the current branch name, but fails for detached HEAD.
+# In that case, git rev-parse will give the current hash.
+original_branch="$(git symbolic-ref --short --quiet HEAD || git rev-parse HEAD)"
+
+local_branch="\
+$(${sed_ext} -e 's/(.*)\..*/\1/' <<< "${basename}").${$}.${RANDOM}"
+
+remote_name=origin
+remote_master_branch_name=master
+remote_master_branch="${remote_name}/${remote_master_branch_name}"
+remote_doc_branch_name=doc
+remote_doc_branch="${remote_name}/${remote_doc_branch_name}"
+
+git fetch
+
+git checkout -b "${local_branch}" "${remote_doc_branch}"
+
+dirty=
+
+function cleanup() {
+  if [[ "${dirty}" ]]; then
+    git reset --hard HEAD
+    git clean --force
+  fi
+
+  git checkout "${original_branch}"
+  git branch -D "${local_branch}"
+}
+
+trap cleanup EXIT
+
+master_hash=$(git rev-parse --short=12 "${remote_master_branch}")
+git merge "${remote_master_branch}" \
+    -m "Merge ${remote_master_branch_name} ${master_hash} into doc"
+
+dirty=y
+
+doc/support/generate.sh
+
+git add -A doc/generated
+
+count="$(git diff --staged --numstat | wc -l)"
+if [[ $count -gt 0 ]]; then
+  git commit \
+      -m "Update documentation to ${remote_master_branch_name} ${master_hash}"
+  dirty=
+
+  git push "${remote_name}" "HEAD:${remote_doc_branch_name}"
+else
+  dirty=
+fi
+
+# cleanup will run on exit