Use calculated fetch depth for versioned source checkout

This should reduce our fetch depth in almost all cases
while still including commits required for versioning
and changelogs and release notes.

Reducing fetch depth saves a lot of time on the checkout
step present in most jobs, so every little bit helps.

Change-type: minor
Signed-off-by: Kyle Harding <[email protected]>

flowzone.yml

@@ -216,7 +216,7 @@
     name: Checkout versioned commit
     uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
     with:
-      fetch-depth: 0
+      fetch-depth: ${{ needs.versioned_source.outputs.depth || 0 }}
       submodules: "recursive"
       # fallback to an invalid ref if the checkout ref is undefined
       ref: "${{ needs.versioned_source.outputs.sha || '¯\_(ツ)_/¯' }}"
@@ -231,7 +231,13 @@
       git fetch origin ${{ github.ref }}
       git checkout FETCH_HEAD -- .github
 
-  - &describeGitState # Resolve tag, semver, sha, and description of current git working copy.
+  # Resolve tag, semver, sha, and description of current git working copy.
+  # tag is the latest tag that points to the current commit.
+  # semver is the semantic version of the tag.
+  # describe is the output of `git describe --tags --always --dirty`.
+  # sha is the full commit hash.
+  # depth is the number of commits since the second most recent tag.
+  - &describeGitState
     name: Describe git state
     id: git_describe
     run: |
@@ -241,6 +247,7 @@
         echo "semver=$(npx -q -y -- semver -c -l "${tag}")" ;
         echo "describe=$(git describe --tags --always --dirty | cat)" ;
         echo "sha=$(git rev-parse HEAD)" ;
+        echo "depth=$(git rev-list "$(git describe --tags --abbrev=0 "$(git rev-list --tags --skip=1 --max-count=1 2>/dev/null)")..HEAD" --count)" ;
       } >> "${GITHUB_OUTPUT}"
 
   - &createLocalRefs
@@ -1103,6 +1110,7 @@ jobs:
       commit_sha: ${{ steps.create_commit.outputs.sha }}
       author: ${{ steps.create_commit.outputs.bot }}
       tag_sha: ${{ steps.create_tag.outputs.sha }}
+      depth: ${{ steps.git_describe.outputs.depth }}
 
     env:
       <<: *gitHubCliEnvironment