From 4fce45a258944817f8e27bb0e1036507ecc8f85f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kl=C3=B6tzke?= <jan@kloetzke.net>
Date: Sat, 9 Mar 2024 17:39:37 +0100
Subject: [PATCH] patch: improve tracking of applied patches

Each applied patch is tracked individually. This has the benefit of
being able to handle situations where multiple patches touch the same
file.

Also remove the check if the patch is still applied. This proved to be
unreliable, especially if multiple patches touch the same file. We now
solely rely on the tracked applied patches and compare them to the
desired ones. If they match, the class will assume the patch is still
applied.

Fixes #55. Fixes #180.
---
 classes/patch.yaml | 60 ++++++++++++++++++++++++++++++++++------------
 1 file changed, 45 insertions(+), 15 deletions(-)

diff --git a/classes/patch.yaml b/classes/patch.yaml
index d159de03..2bbeda91 100644
--- a/classes/patch.yaml
+++ b/classes/patch.yaml
@@ -26,24 +26,54 @@ checkoutSetup: |
         # Skip if series is already applied. Otherwise try to remove old series if
         # it does not match.
         name=".applied$name"
-        if [ -e "$name" ] ; then
-            if cmp <( for (( idx=$# ; idx>0 ; idx-- )) ; do cat "${@:$idx:1}" ; done ) "$name" ; then
-                # The patch is allegedly applied and was not changed. Check if
-                # it is still applied as expected...
-                if patch -p $p -F 0 -Rfs --dry-run < "$name" ; then
-                    return
-                fi
-                echo "Patch was (partially) squashed? Trying to recover..." >&2
-            fi
-            # Remove old patch
+        if [ -f "$name" ] ; then
+            # Remove old patch that was applied by an older version of this
+            # class. It's tracking is incompatible with the current version!
             patch -p $p -F 0 -Rf < "$name" || true
             rm "$name"
+        elif [ -r "$name/series" ] ; then
+            local -a applied
+            local need_revert=no
+
+            readarray -t applied < "$name/series"
+            if [[ $# -ne ${#applied[@]} ]] ; then
+                # Different number of patches -> revert
+                need_revert=yes
+            else
+                # Compare each patch to see if still unchanged
+                for (( i=0 ; i<$# ; i++ )) ; do
+                    cmp "$name/${applied[$i]}" "${@:((i+1)):1}" || need_revert=yes
+                done
+            fi
+
+            if [[ $need_revert = yes ]] ; then
+                # Remove old patch series in reverse order
+                for (( i=${#applied[@]}-1; i>=0; i--)) ; do
+                    patch -p $p -Rf < "$name/${applied[$i]}"
+                    rm "$name/${applied[$i]}"
+                    unset applied[$i]
+                    printf "%s\n" "${applied[@]}" > "$name/series"
+                done
+                rm "$name/series"
+            else
+                # Patch is presumably still applied. Move on...
+                return 0
+            fi
         fi
 
-        for i in "$@" ; do
-            patch -p $p -F 0 -f < $i
-            touch "$name"
-            cat $i "$name" > "$name".new
-            mv "$name".new "$name"
+        # Apply patches and track them in the series file
+        mkdir -p "$name"
+        for (( i=1 ; i<=$# ; i++ )) ; do
+            local fn="${@:$i:1}"
+            local subject="$( sed -n -e '/^Subject: /{
+                                            s/^Subject: //          # strip subject
+                                            s/^\[PATCH[^]]*\] //    # strip any PATCH tag
+                                            s/[^a-zA-Z0-9]/-/g      # only keep letters and numbers
+                                            p; q                    # one is enough
+                                        }' "$fn" )"
+            subject="$(printf "%04d-%s.patch" $i "$subject")"
+            patch -p $p -F 0 -f < "$fn"
+            cp "$fn" "$name/$subject"
+            echo "$subject" >> "$name/series"
         done
     }