docs(ci): Netlify ignore command to check branch (zmkfirmware#2659)

Add a separate ignore script that checks git changes but also
only deploys main and version branches to allow us to deploy
versioned docs.

Co-authored-by: Cem Aksoylar <[email protected]>

Author: petejohanson

docs/netlify-ignore-command.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+# We deploy main, version branches and deploy previews only
+if echo $HEAD | grep -E '^(main|v[[:digit:]]+\.([[:digit:]])+-branch)$' || echo $CONTEXT | grep '^deploy-preview$'
+then
+  echo "Head '$HEAD' matches a deployed branch, or context is deploy preview, checking for git changes."
+  git diff --quiet $CACHED_COMMIT_REF $COMMIT_REF . ../app/boards/
+else
+  echo "Head '$HEAD' does not match a deployed branch and is not a deploy preview"
+  exit 0
+fi

docs/netlify.toml

@@ -1,5 +1,5 @@
 [build]
-  ignore = "git diff --quiet $CACHED_COMMIT_REF $COMMIT_REF . ../app/boards/"
+  ignore = "bash ./netlify-ignore-command.sh"
 
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