Our GitHub Action should ignore diff/*.pdf errors

Due to unchanged nearby tables and other reasons, latexdiff will sometimes
spuriously fail. CI should succeed nonetheless and just omit the diff PDF.
This is why we use `make -k`, but it does not affect make's exit status.

Extend run.sh so that it can ignore exit statuses. We could have just
used `make -i` or arranged to use `-latexdiff-vc` in the recipe, but doing
this in run.sh allows us to separate the two `make` commands so they are
tidily interleaved with their output in the logs.

(Somewhat unfortunately because action arguments can't be lists of strings
this increases the coupling between pr-pdfs.yaml and action.yaml.)

.github/actions/texlive/action.yaml

@@ -2,13 +2,16 @@ name: texlive
 description: Run commands in a TeXLive docker image
 
 inputs:
-  run:
-    description: Commands to be executed
+  run1:
+    description: Commands to be executed first
     required: true
+  run2:
+    description: Commands to be executed second
 
 runs:
   using: docker
   image: docker://texlive/texlive:latest
   entrypoint: .github/actions/texlive/run.sh
   args:
-    - ${{ inputs.run }}
+    - ${{ inputs.run1 }}
+    - ${{ inputs.run2 }}

.github/actions/texlive/run.sh

@@ -11,7 +11,13 @@ git config --global --add safe.directory "$GITHUB_WORKSPACE" || exit
 
 for cmd
 do
+    mode=
+    case "$cmd" in
+    -*) mode=" (ignoring errors)"
+        cmd="${cmd#-}"
+    esac
+
     echo
-    echo "[command]$cmd"
-    eval "$cmd" || exit
+    echo "[command]$cmd$mode"
+    eval "$cmd" || test -n "$mode" || exit
 done

.github/workflows/pr-pdfs.yaml

@@ -34,7 +34,8 @@ jobs:
         uses: ./.github/actions/texlive
         if:   ${{ env.changed }}
         with:
-          run: make ${{ env.pdfs }} && make -k OLD=$mergebase_sha NEW=HEAD ${{ env.diffs }}
+          run1: make ${{ env.pdfs }}
+          run2: -make -k OLD=$mergebase_sha NEW=HEAD ${{ env.diffs }}
 
       - uses: actions/upload-artifact@v3
         with: