checkout: helper script for checking out branches and tags

Signed-off-by: Thilo Fromm <thilo@kinvolk.io>

checkout

@@ -0,0 +1,171 @@
+#!/bin/bash
+#
+# Copyright (c) 2021 The Flatcar Maintainers.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+set -eu
+
+force_tag="false"
+force_branch="false"
+
+update_strategy="fast-forward"
+
+name=""
+
+usage() {
+    echo "  Usage:"
+    echo "  $0 [-t|-b] [-n] [-u <strategy>] <tag-or-branch>"
+    echo "       Check our a tag or branch and synchronise git submodules"
+    echo "          coreos-overlay and portage-stable."
+    echo "       By default, $0 tries to auto-detect whether to handle a tag or a branch,"
+    echo "         with tags being prioritised over branches of the same name."
+    echo
+    echo "       <tag-or-branch> Name of the tag or branch to check out."
+    echo "                       BRANCH: Check out the branch in scripts, coreos-overlay"
+    echo "                                and portage-stable, and fast-forward to the"
+    echo "                                latest changes by default (but see '-u' below)."
+    echo "                       TAG:    Check out the tag in scripts, and update submodules."
+    echo
+    echo "       -t            force TAG mode. Branches of the given name are ignored."
+    echo "                      Mutually exclusive with '-b'."
+    echo "       -b            force BRANCH mode. Tags of the given name are ignored."
+    echo "                      Mutually exclusive with '-t'."
+    echo
+    echo "       -u <strategy> Only applies to BRANCH checkouts."
+    echo "                      When checking out submodule branches, use <strategy>."
+    echo "                      instead of fast-forward. Strategy is one of:"
+    echo "                      'fast-forward' - fast-forward to upstream branch tip. Default."
+    echo "                      'rebase' - rebase local changes on upstream changes."
+    echo "                                 Useful for keepling local changes in submodules."
+    echo "                      'omit'   - check out branches, but do not update."
+    echo "                      Defaults to '$update_strategy'"
+    echo
+    echo "       -h            Print this help."
+    echo
+}
+# --
+
+while [ 0 -lt $# ] ; do
+    case "$1" in
+    -h) usage; exit 0;;
+    -t) force_tag="true";     shift;;
+    -b) force_branch="true";  shift;;
+    -u) update_strategy="$2"; shift; shift;;
+    *) if [ -n "$name" ] ; then
+            echo
+            echo "ERROR: only ONE tag-or-branch can be specified."
+            echo
+            usage
+            exit 1
+       fi
+       name="$1";      shift;;
+    esac
+done
+
+if [ -z "$name" ] ; then
+    usage
+    exit 0
+fi
+
+if $force_branch && $force_tag; then
+    echo
+    echo "ERROR: '-t' and '-b' are mutually exclusive. Please make up your mind."
+    echo
+    usage
+    exit 1
+fi
+
+case "$update_strategy" in
+    fast-forward) update_strategy="--ff-only";;
+    rebase)       update_strategy="--rebase";;
+    omit)         update_strategy="";;
+    *)  echo
+        echo "ERROR: unsupported branch update strategy '$update_strategy'."
+        echo
+        usage
+        exit 1;;
+esac
+# --
+
+# make sure submodules are initialised
+git submodule init
+for dir in sdk_container/src/third_party/coreos-overlay \
+           sdk_container/src/third_party/portage-stable ; do
+    if [ ! -f "$dir"/.git ] ; then
+        git submodule update -N "$dir"
+    fi
+done
+
+function check_all() {
+    local gitcmd="$1"
+    local name="$2"
+
+    local scripts="$(git $gitcmd \
+                        | sed -e 's/^[[:space:]]*//' -e 's:remotes/[^/]\+/::' \
+                        | grep -m1 -E "^$name\$")"
+    local overlay="$(git -C sdk_container/src/third_party/coreos-overlay $gitcmd \
+                        | sed -e 's/^[[:space:]]*//' -e 's:remotes/[^/]\+/::' \
+                        | grep -m1 -E "^$name\$")"
+    local portage="$(git -C sdk_container/src/third_party/portage-stable $gitcmd \
+                        | sed -e 's/^[[:space:]]*//' -e 's:remotes/[^/]\+/::' \
+                        | grep -m1 -E "^$name\$")"
+
+    if [ -n "$scripts" -a -n "$overlay" -a -n "$portage" ] ; then
+        echo "$scripts"
+    fi
+}
+# --
+
+#
+# TAG
+#
+if ! $force_branch; then
+    for dir in . \
+        sdk_container/src/third_party/coreos-overlay \
+        sdk_container/src/third_party/portage-stable ; do
+        git -C "$dir" fetch --tags --force --prune --prune-tags
+    done
+    tag="$(check_all 'tag -l' "$name")"
+
+    if [ -n "$tag" ] ; then
+        echo
+        echo "Checking out TAG '$tag'"
+        echo "----------------------------------"
+        git checkout "$tag"
+        git submodule update
+        exit
+    fi
+fi
+
+echo "No tag by name '$name' in repo + submodules."
+
+if $force_tag; then
+    echo "Tag-only mode forced, exiting."
+    exit 1
+fi
+
+#
+# BRANCH
+#
+
+branch="$(check_all "branch -a -l" "$name")"
+if [ -z "$branch" ]; then
+    echo "No branch by name '$name' in repo + submodules."
+    exit 1
+fi
+
+echo
+echo "Checking out BRANCH '$branch'"
+echo "----------------------------------"
+for dir in . \
+    sdk_container/src/third_party/coreos-overlay \
+    sdk_container/src/third_party/portage-stable ; do
+
+    git -C "$dir" checkout "$branch"
+    if [-n "$update_strategy" ] ; then
+        echo "updating branch in '$dir' /'$update_strategy')"
+        git -C "$dir" pull "$update_strategy"
+    fi
+done
+