Add support for a custom tag prefix

action.yml

@@ -6,7 +6,7 @@ inputs:
     description: Path to changelog
     required: false
   title:
-    description: Format of title (variables `$tag`, `$version`, and any string)
+    description: Format of title (variables `$tag`, `$version`, `$prefix`, and any string)
     required: false
     default: '$tag'
   draft:
@@ -16,6 +16,19 @@ inputs:
   branch:
     description: Reject releases from commits not contained in branches that match the specified pattern (regular expression)
     required: false
+  prefix:
+    description: >
+      A prefix for the release tag, before the version number (for
+      example, 'my-crate-v0.1.2' has the prefix 'my-crate-').
+
+      The prefix may not contain regular expression characters such as `\`, `.`,
+      `(`, `)`, `[`, `]`, `{` and `}`.
+
+      If the prefix ends in a trailing '-', it will be stripped before
+      interpolating the prefix into the title, if `$prefix` appears in the title
+      format.
+    required: false
+    default: ''
 
 runs:
   using: node12

main.sh

@@ -17,6 +17,7 @@ title="${INPUT_TITLE:?}"
 changelog="${INPUT_CHANGELOG:-}"
 draft="${INPUT_DRAFT:-}"
 branch="${INPUT_BRANCH:-}"
+prefix="${INPUT_PREFIX:-}"
 
 if [[ -z "${GITHUB_TOKEN:-}" ]]; then
     error "GITHUB_TOKEN not set"
@@ -29,17 +30,26 @@ if [[ "${GITHUB_REF:?}" != "refs/tags/"* ]]; then
 fi
 tag="${GITHUB_REF#refs/tags/}"
 
-# TODO: Support custom prefix of tags https://github.com/taiki-e/create-gh-release-action/issues/1
-if [[ ! "${tag}" =~ ^v?[0-9]+\.[0-9]+\.[0-9]+(-[a-zA-Z_0-9\.-]+)?(\+[a-zA-Z_0-9\.-]+)?$ ]]; then
+if [[ "${prefix}" =~ (\\|\$|\[|\]|\*|\||\{|\}|\+|\?|\^|\(|\)|\.)+ ]]; then
+    error "prefix '${prefix}' contained regular expression characters"
+    exit 1
+fi
+
+if [[ ! "${tag}" =~ ^${prefix}v?[0-9]+\.[0-9]+\.[0-9]+(-[a-zA-Z_0-9\.-]+)?(\+[a-zA-Z_0-9\.-]+)?$ ]]; then
     error "invalid tag format: '${tag}'"
     exit 1
 fi
-if [[ "${tag}" =~ ^v?[0-9\.]+-[a-zA-Z_0-9\.-]+(\+[a-zA-Z_0-9\.-]+)?$ ]]; then
+if [[ "${tag}" =~ ^${prefix}v?[0-9\.]+-[a-zA-Z_0-9\.-]+(\+[a-zA-Z_0-9\.-]+)?$ ]]; then
     prerelease="--prerelease"
 fi
-version="${tag#v}"
+version="${tag#${prefix}v}"
+# if the prefix has a trailing slash, strip it so that the prefix can be used in
+# the title.
+prefix="${prefix#-}"
 title="${title/\$tag/${tag}}"
 title="${title/\$version/${version}}"
+title="${title/\$prefix/${prefix}}"
+
 
 case "${draft}" in
     true) draft_option="--draft" ;;