Add script to merge remote patches

2 files changed, 84 insertions, 7 deletions

diff --git a/gitmirror-merge.sh b/gitmirror-merge.sh
new file mode 100755
index 0000000..d346602
--- /dev/null
+++ b/gitmirror-merge.sh
@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+
+MIRROR_REMOTE="gitmirror_remote"
+CLONE_URL_PATTERN="file://${PWD}/%s"
+
+msg() {
+    echo "==> $1"
+}
+
+msg2() {
+    echo "--> $1"
+}
+
+deepened_fetch() {
+    local fetch_spec="$1"
+    local exclude="$2"
+    if git fetch "${MIRROR_REMOTE}" "${fetch_spec}" \
+        --shallow-exclude="${exclude}"; then
+        msg2 "Deepen fetch by 1"
+        git fetch "${MIRROR_REMOTE}" "${fetch_spec}" --deepen=1
+    else
+        msg2 "Shallow request possibly empty, retry with depth=1"
+        git fetch "${MIRROR_REMOTE}" "${fetch_spec}" --depth=1
+    fi
+}
+
+merge_patches() {
+    if (( $# != 3 )); then
+        echo "Usage: $0 REPOSITORY REMOTE BRANCH" >&2
+        exit 1
+    fi
+
+    local repository="$1"
+    local remote="$2"
+    local branch="$3"
+
+    if [[ "${remote}" == "${MIRROR_REMOTE}" ]]; then
+       msg "REMOTE must not be ${MIRROR_REMOTE}" >&2
+       exit 1
+    fi
+
+    local copy_name="${repository}-patch-${remote}-${branch}"
+    msg "Create working copy ${copy_name}"
+    rm -rf "${copy_name}"
+    mkdir "${copy_name}"
+    pushd "${copy_name}" > /dev/null
+    git init
+    local clone_url
+    # shellcheck disable=2059
+    clone_url="$(printf "${CLONE_URL_PATTERN}" "${repository}")"
+    git remote add "${MIRROR_REMOTE}" "${clone_url}"
+
+    local patch_branch="patch-for/${branch}"
+    msg "Fetch patch at ${patch_branch}"
+    local upstream_branch="${remote}/${branch}"
+    local remote_upstream_ref="refs/remotes/${upstream_branch}"
+    deepened_fetch "${patch_branch}" "${remote_upstream_ref}"
+
+    msg "Fetch upstream at ${upstream_branch}"
+    local local_upstream_ref="refs/remotes/${MIRROR_REMOTE}/${upstream_branch}"
+    deepened_fetch "${remote_upstream_ref}:${local_upstream_ref}" \
+        "refs/heads/${patch_branch}"
+
+    msg "Merge ${patch_branch} into ${upstream_branch}"
+    git checkout -b "${branch}" --no-track "${local_upstream_ref}"
+    git merge "${MIRROR_REMOTE}/${patch_branch}" --no-ff \
+        -m "Merge branch '${patch_branch}' into ${upstream_branch}"
+
+    msg "Push ${branch} to ${MIRROR_REMOTE}"
+    git push --force "${MIRROR_REMOTE}" "${branch}:${branch}"
+
+    popd > /dev/null
+    rm -rf "${copy_name}"
+}
+
+if [[ "$0" == "${BASH_SOURCE[0]}" ]]; then
+    merge_patches "$@"
+fi
diff --git a/gitmirror.sh b/gitmirror.sh
index 29503d9..53433dc 100755
--- a/gitmirror.sh
+++ b/gitmirror.sh
@@ -22,6 +22,8 @@ read_branches() {
     done < <(git for-each-ref "${prefix}**" \
         --format=$'%(refname)\t%(objectname)' \
         --color=never)
+
+    local branch_name
     for branch_name in "${!read_branches_target[@]}"; do
         printf "    %*s = %s\n" \
             $((-max_length)) \
@@ -55,18 +57,14 @@ archive_if_needed() {
 }
 
 sync_mirror() {
-    if (( $# == 0 || $# > 2 )); then
+    if (( $# != 2 )); then
         echo "Usage: $0 REPOSITORY [REMOTE]" >&2
         exit 1
     fi
 
     local repository="$1"
-    local remote
-    if (( $# == 1 )); then
-        remote="origin"
-    else
-        remote="$2"
-    fi
+    local remote="$2"
+
     local archive_prefix
     archive_prefix="$(TZ='UTC' printf 'archives/%(%Y%m%dT%H%M%S)TZ/')"