feat: improve patch updating

apatch

@@ -1,10 +1,8 @@
 #!/bin/sh
 
 startdir="$PWD"
-patch_exists=0
 
 [ -f APKBUILD ] || ( echo "please run this in a package directory"; exit 1 )
-[ -f "$1" ] && patch_exists=1
 [ "$1" != "" ] || ( echo "usage: apatch <patch name>"; exit 1 )
 
 abuild clean fetch unpack prepare
@@ -14,10 +12,24 @@ abuild clean fetch unpack prepare
 [ -z "$builddir" ] && builddir="/$pkgname-$pkgver"
 
 cp -r src src-old
+
+for patch in $source; do
+  if [ "$patch" = "$1" ]; then
+    # if the patch was in source, it was already applied in prepare() above,
+    # but we want the original src to not have it, so we can get a full diff of
+    # its original changes + our new ones
+    (
+      cd "src-old/$builddir"
+      patch -R -p1 < "$startdir/$1"
+    )
+    break
+  fi
+done
+
 (
   cd "src$builddir"
-  [ "$patch_exists" -eq 1 ] && patch -p1 < "$startdir/$1"
   $SHELL
 )
+
 busybox diff -U3 -r "src-old$builddir" "src$builddir" | sed "s|src-old$builddir|a|g;s|src$builddir|b|g" > $1
 rm -rf src-old