attempt to checkout the PR's branch

This commit adds some debugging (to print the full JSON github context vars) and attempts to checkout the head ref before attempting to do a diff. Hopefully this will fix issues of "object not found" because the diff is currently being done in the repo's default branch (main or master), but that won't work if the PR is being submitted to a different branch (eg 'dev') or, maybe, if the PR is being submitted from a different branch.

See also

 * https://stackoverflow.com/questions/70104600/complete-list-of-github-actions-contexts
 * #4
 * BusKill/buskill-app#90 (comment)

Author: maltfield

.github/workflows/unicode_warn.yml

@@ -1,6 +1,6 @@
 ################################################################################
 # File:    .github/workflows/unicode_warn.yml
-# Version: 0.3
+# Version: 0.4
 # Purpose: Detects Unicode in PRs and comments the results of findings in PR
 # Authors: Michael Altfield <michael@michaelaltfield.net>
 # Created: 2021-11-20
@@ -26,6 +26,11 @@ jobs:
       pull-requests: write
 
     steps:
+
+    - name: Dump GitHub context
+      env:
+        GITHUB_CONTEXT: ${{ toJSON(github) }}
+      run: echo "$GITHUB_CONTEXT"
 
     - name: Prereqs
       env:
@@ -45,6 +50,9 @@ jobs:
         git config --global --add safe.directory "$(pwd)"
         git branch -a
         git log
+        git checkout ${{ github.event.pull_request.head.ref }}
+        git branch -a
+        git log
 
         diff=`git diff --unified=0 ${{ github.event.pull_request.base.sha }} ${{ github.event.pull_request.head.sha }} | grep -E "^[+]" | grep -Ev '^(--- a/|\+\+\+ b/)'`
         if [ $? -ne 0 ]; then