Storing the output of the build in tmp files so we can extract

the bits we need
But we need both main and branch checked out and the action can
do it for us
Pulling the bank occupancy from the map produced by sdcc rather
than the output of the build as it appears the output number is
only the maximum size of the banks
BANK0 isn't output, but what I'm guessing are the consituents for it are

.github/workflows/build.yml

@@ -5,6 +5,10 @@ on:
     branches: ['**']
   pull_request:
 
+permissions:
+  contents: read
+  pull-requests: write
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -13,18 +17,48 @@ jobs:
 
     steps:
       - uses: actions/checkout@v6
+        with:
+          path: branch
+
+      - uses: actions/checkout@v6
+        with:
+          path: main
+          ref: main
 
       - name: Install dependencies
         run: |
           apt update
           apt install make gcc sdcc xxd python-is-python3 libjson-c-dev zlib1g-dev -y
       - name: Run the host-side unit tests
-        run: make -C test
+        run: cd branch && make -C test
       - name: Check that every machine definition can be compiled
-        run: make machine_check
+        run: cd branch && make machine_check
       - name: Make project (4x2/RTL8372)
-        run: make CI=1 MACHINE="KP_9000_6XHML_X2"
+        run: cd branch && make CI=1 MACHINE="KP_9000_6XHML_X2" && cp output/KP_9000_6XHML_X2/rtlplayground.map /tmp/branch.map
       - name: Make project (8x1/RTL8373)
-        run: make CI=1 MACHINE="KP_9000_9XHML_X_V3_1"
+        run: cd branch && make CI=1 MACHINE="KP_9000_9XHML_X_V3_1"
       - name: Make project with the health instrumentation
-        run: make clean && make CI=1 MACHINE="KP_9000_6XHML_X2" HEALTH=1
+        run: cd branch && make clean && make CI=1 MACHINE="KP_9000_6XHML_X2" HEALTH=1
+      - name: Make main
+        run: cd main && make CI=1 MACHINE="KP_9000_6XHML_X2" && cp output/KP_9000_6XHML_X2/rtlplayground.map /tmp/main.map
+      - name: Calculate bank growth
+        run: |
+          sed -rn 's/^([XCD]SEG|(BANK[0-9])).*=\s+([0-9]+)\. bytes.*$/MAIN_\1=\3/p' /tmp/main.map | sort | uniq >> "$GITHUB_ENV"
+          sed -rn 's/^([XCD]SEG|(BANK[0-9])).*=\s+([0-9]+)\. bytes.*$/BRANCH_\1=\3/p' /tmp/branch.map | sort | uniq >> "$GITHUB_ENV"
+      - name: Update PR comment
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          header: Sizes
+          message: |
+            ## Image Growth
+
+            Commit: ${{ github.sha }}
+
+            | Bank # | Main | Branch |
+            | --- | --- | --- |
+            | XSEG | ${{ env.MAIN_XSEG }} bytes | ${{ env.BRANCH_XSEG }} bytes |
+            | CSEG | ${{ env.MAIN_CSEG }} bytes | ${{ env.BRANCH_CSEG }} bytes |
+            | DSEG | ${{ env.MAIN_DSEG }} bytes | ${{ env.BRANCH_DSEG }} bytes |
+            | 1 | ${{ env.MAIN_BANK1 }} bytes | ${{ env.BRANCH_BANK1 }} bytes |
+            | 2 | ${{ env.MAIN_BANK2 }} bytes | ${{ env.BRANCH_BANK2 }} bytes |
+            | 3 | ${{ env.MAIN_BANK3 }} bytes | ${{ env.BRANCH_BANK3 }} bytes |