Add use_api feature

So that you don't _need_ to checkout (clone) the repo to the worker

action.yml

@@ -26,6 +26,10 @@ inputs:
     description: 'Specify a non-default branch to use for the release tag (the one without -pre)'
     required: false
     type: string
+  use_api:
+    description: 'Use the GitHub API to discover current tags, which avoids the need for a git checkout, but requires `curl` and `jq`'
+    required: false
+    default: false
 
 outputs:
   current-version:
@@ -69,7 +73,9 @@ runs:
       run: ${{ github.action_path }}/version-lookup.sh
       shell: bash
       env:
+        github_token: ${{ github.token }}
         scheme: ${{ inputs.scheme }}
+        use_api: ${{ inputs.use_api }}
 
     - id: version-increment
       run: ${{ github.action_path }}/version-increment.sh
@@ -77,6 +83,8 @@ runs:
       env:
         current_version: ${{ steps.version-lookup.outputs.CURRENT_VERSION }}
         increment: ${{ inputs.increment }}
+        github_token: ${{ github.token }}
         pep440: ${{ inputs.pep440 }}
         scheme: ${{ inputs.scheme }}
         release_branch: ${{ inputs.release_branch }}
+        use_api: ${{ inputs.use_api }}

shared.sh

@@ -27,6 +27,20 @@ if [[ "${pep440}" != 'false' && "${pep440}" != 'true' ]] ; then
     input_errors='true'
 fi
 
+use_api="${use_api:-false}"
+if [[ "${use_api}" != 'false' && "${use_api}" != 'true' ]] ; then
+    echo "🛑 Value of 'use_api' is not valid, choose from 'false' or 'true'" 1>&2
+    input_errors='true'
+fi
+
+if [[ "${use_api}" == 'true' ]] ; then
+    if [[ -z "${github_token:-}" ]] ; then
+        echo "🛑 'use_api' is true, but environment variable 'github_token' is not set" 1>&2
+        input_errors='true'
+    fi
+fi
+
+
 ##==----------------------------------------------------------------------------
 ##  MacOS compatibility - for local testing
 

version-increment.sh

@@ -28,20 +28,34 @@ fi
 ##  Git info - branch names, commit short ref
 
 default_branch='main'
-# if we're _not_ testing, then _actually_ check the origin
-if [[ -z "${BATS_VERSION:-}" ]] ; then
-    default_branch="$(git remote show origin | ${grep} 'HEAD branch' | cut -d ' ' -f 5)"
-fi
 # use release_branch if not empty
 if [[ -n "${release_branch:-}" ]] ; then
     default_branch="${release_branch}" 
+elif [[ -z "${BATS_VERSION:-}" ]] ; then
+    # if we're _not_ testing, then _actually_ check the origin
+    if [[ "${use_api:-}" == 'true' ]] ; then
+        default_branch="$(
+            curl -fsSL \
+                -H "Accept: application/vnd.github+json" \
+                -H "Authorization: Bearer ${github_token}" \
+                -H "X-GitHub-Api-Version: 2022-11-28" \
+                "${GITHUB_API_URL}/repos/${GITHUB_REPOSITORY}" \
+            | jq -r '.default_branch'
+        )"
+    else
+        default_branch="$(git remote show origin | ${grep} 'HEAD branch' | cut -d ' ' -f 5)"
+    fi
 fi
 
 current_ref="${GITHUB_REF:-}"
-git_commit="$(git rev-parse --short HEAD | sed 's/0*//')"  # trim leading zeros, because semver doesn't allow that in
-                                                           # the 'pre-release version' part, but we can't use the + char
-                                                           # to make it 'build metadata' as that's not supported in K8s
-                                                           # labels
+
+if [[ "${use_api:-}" == 'true' ]] ; then
+    # because we cannot use `rev-parse` with the API, we'll take a punt that 9 characters is enough for uniqueness
+    # shellcheck disable=SC2001
+    git_commit="$(echo "${GITHUB_SHA:0:9}" | sed 's/0*//')"    # Also, trim leading zeros, because semver doesn't allow that in
+else                                                           # the 'pre-release version' part, but we can't use the + char
+    git_commit="$(git rev-parse --short HEAD | sed 's/0*//')"  # to make it 'build metadata' as that's not supported in K8s
+fi                                                             # labels
 
 ##==----------------------------------------------------------------------------
 ##  Version increment

version-lookup.sh

@@ -25,16 +25,33 @@ fi
 ##==----------------------------------------------------------------------------
 ##  Get tags from GitHub repo
 
-# Skip if testing, otherwise pull tags
+# Skip if testing, or if use_api is true, otherwise pull tags
 if [[ -z "${BATS_VERSION:-}" ]] ; then
-    git fetch --quiet --force origin 'refs/tags/*:refs/tags/*'
+    if [[ "${use_api:-}" != 'true' ]] ; then
+        git fetch --quiet --force origin 'refs/tags/*:refs/tags/*'
+    fi
 fi
 
 ##==----------------------------------------------------------------------------
 ##  Version parsing
 
 # detect current version - removing "v" from start of tag if it exists
-current_version="$(git tag -l | { ${grep} -P "${pcre_allow_vprefix}" || true; } | sed 's/^v//g' | sort -V | tail -n 1)"
+if [[ "${use_api:-}" == 'true' ]] ; then
+    current_version="$(
+        curl -fsSL \
+            -H "Accept: application/vnd.github+json" \
+            -H "Authorization: Bearer ${github_token}" \
+            -H "X-GitHub-Api-Version: 2022-11-28" \
+            "${GITHUB_API_URL}/repos/${GITHUB_REPOSITORY}/git/matching-refs/tags/" \
+        | jq -r '.[].ref' | sed 's|refs/tags/||g' \
+        | { ${grep} -P "${pcre_allow_vprefix}" || true; } | sed 's/^v//g' | sort -V | tail -n 1
+    )"
+else
+    current_version="$(
+        git tag -l \
+        | { ${grep} -P "${pcre_allow_vprefix}" || true; } | sed 's/^v//g' | sort -V | tail -n 1
+    )"
+fi
 
 # support transition from an old reecetech calver style (yyyy-mm-Rr, where R is the literal `R`, and r is the nth release for the month)
 if [[ -z "${current_version:-}" ]] ; then