handle multi-line dagger shell blocks (#203)

Signed-off-by: kpenfound <kyle@dagger.io>

Author: kpenfound

.github/workflows/test.yml

@@ -236,6 +236,58 @@ jobs:
             exit 1
           fi
 
+  call-multiline-backslash:
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: actions/checkout@v4
+      - name: "Test call with backslash continuation"
+        id: test-call-backslash
+        uses: ./
+        with:
+          version: latest
+          verb: core
+          args: |-
+            container \
+            from --address=alpine \
+            with-exec --args echo,-n,"hello world" \
+            stdout
+      - name: "Test call backslash (check)"
+        run: |
+          target='${{ steps.test-call-backslash.outputs.output }}'
+          if [[ "$target" == "hello world" ]]; then
+            echo "matches"
+            exit 0
+          else
+            echo "does not match: $target"
+            exit 1
+          fi
+
+  call-multiline-newline:
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: actions/checkout@v4
+      - name: "Test call with bare newlines"
+        id: test-call-newline
+        uses: ./
+        with:
+          version: latest
+          verb: core
+          args: |-
+            container
+            from --address=alpine
+            with-exec --args echo,-n,"hello world"
+            stdout
+      - name: "Test call newline (check)"
+        run: |
+          target='${{ steps.test-call-newline.outputs.output }}'
+          if [[ "$target" == "hello world" ]]; then
+            echo "matches"
+            exit 0
+          else
+            echo "does not match: $target"
+            exit 1
+          fi
+
   check:
     runs-on: "ubuntu-latest"
     steps:

action.yml

@@ -133,10 +133,11 @@ runs:
       run: |
         verb=${{ inputs.verb }}
         shell=$(echo '${{ toJSON(inputs.shell) }}' | jq -rj .)
-        dagger_flags=$(echo '${{ toJSON(inputs.dagger-flags) }}' | jq -rj .)
-        args=$(echo '${{ toJSON(inputs.args) }}' | jq -rj .)
-        call=$(echo '${{ toJSON(inputs.call) }}' | jq -rj .)
-        check=$(echo '${{ toJSON(inputs.check) }}' | jq -rj .)
+        # Collapse backslash-continuations and newlines into spaces for CLI args
+        dagger_flags=$(echo '${{ toJSON(inputs.dagger-flags) }}' | jq -rj . | sed -z 's/\\\n/ /g; s/\n/ /g')
+        args=$(echo '${{ toJSON(inputs.args) }}' | jq -rj . | sed -z 's/\\\n/ /g; s/\n/ /g')
+        call=$(echo '${{ toJSON(inputs.call) }}' | jq -rj . | sed -z 's/\\\n/ /g; s/\n/ /g')
+        check=$(echo '${{ toJSON(inputs.check) }}' | jq -rj . | sed -z 's/\\\n/ /g; s/\n/ /g')
         if [[ -n "${{ inputs.call }}" ]]; then
           verb="call"
         elif [[ -n "$check" ]]; then