From f57dd91035d1963566bd835dfe9c24a1897addb2 Mon Sep 17 00:00:00 2001
From: SpiritCroc <dev@spiritcroc.de>
Date: Sat, 3 Sep 2022 18:19:55 +0200
Subject: [PATCH] merge_helpers.sh: depend less on upstream tags

Change-Id: Ic79931eba7d501e4f76e5dd069921f9f3486f86c
---
 merge_helpers.sh | 68 +++++++++++++++++++++++++++++++++++++++++++++---
 pre_merge.sh     |  2 +-
 2 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/merge_helpers.sh b/merge_helpers.sh
index fcbade32fa..218b691281 100755
--- a/merge_helpers.sh
+++ b/merge_helpers.sh
@@ -22,6 +22,52 @@ require_clean_git() {
     fi
 }
 
+upstream_common_base() {
+    local base="$1"
+    if [ -z "$base" ]; then
+        local base="HEAD"
+    fi
+    local merged_develop=`git merge-base "$base" upstream/develop`
+    local merged_main=`git merge-base "$base" upstream/main`
+    >&2 echo "Last merged main: $(git log -1 --oneline "$merged_main")"
+    >&2 echo "Last merged develop: $(git log -1 --oneline "$merged_develop")"
+    # Is latest main or develop merge more up-to-date?
+    if [ "$merged_develop" = "$merged_main" ]; then
+        >&2 echo "Last merged: upstream/main = upstream/develop"
+        commit="$merged_main"
+    elif git merge-base --is-ancestor "$merged_develop" "$merged_main"; then
+        >&2 echo "Last merged: upstream/main > upstream/develop"
+        commit="$merged_main"
+    elif git merge-base --is-ancestor "$merged_main" "$merged_develop"; then
+        >&2 echo "Last merged: upstream/develop > upstream/main"
+        commit="$merged_develop"
+    else
+        # Commented out: code works (I think), but may be safer to not assume such things
+        #develop_timestamp=`git show -s --format=%ct "$merged_develop"`
+        #main_timestamp=`git show -s --format=%ct "$merged_main"`
+        #if ((develop_timestamp > main_timestamp)); then
+        #    >&2 echo "Last merged: upstream/develop (later ts)"
+        #    commit="$merged_develop"
+        #elif ((develop_timestamp < main_timestamp)); then
+        #    >&2 echo "Last merged: upstream/main (later ts)"
+        #    commit="$merged_main"
+        #else
+            >&2 echo "ERROR: don't know how to compare main and develop upstream branches"
+            exit 1
+        #fi
+    fi
+    echo "$commit"
+}
+
+upstream_previous_common_base() {
+    local base="$(upstream_common_base 2>/dev/null)"
+    if [ -z "$base" ]; then
+        >&2 echo "ERROR: don't know how to compare main and develop upstream branches"
+        exit 1
+    fi
+    upstream_common_base "$base~1"
+}
+
 upstream_latest_tag() {
     git describe --abbrev=0 upstream/main --tags
 }
@@ -44,13 +90,27 @@ downstream_latest_tag() {
 }
 
 upstream_diff() {
-    local latest_tag=`upstream_latest_tag`
-    local previous_tag=`upstream_previous_tag`
+    #local latest_tag=`upstream_latest_tag`
+    #local previous_tag=`upstream_previous_tag`
+    if git rev-parse MERGE_HEAD > /dev/null; then
+        local latest_tag=`git rev-parse MERGE_HEAD`
+        local previous_tag=`upstream_common_base`
+    else
+        local latest_tag=`upstream_common_base`
+        local previous_tag=`upstream_previous_common_base`
+    fi
     git diff "$previous_tag".."$latest_tag" "$@"
 }
 upstream_log() {
-    local latest_tag=`upstream_latest_tag`
-    local previous_tag=`upstream_previous_tag`
+    #local latest_tag=`upstream_latest_tag`
+    #local previous_tag=`upstream_previous_tag`
+    if git rev-parse MERGE_HEAD > /dev/null; then
+        local latest_tag=`git rev-parse MERGE_HEAD`
+        local previous_tag=`upstream_common_base`
+    else
+        local latest_tag=`upstream_common_base`
+        local previous_tag=`upstream_previous_common_base`
+    fi
     git log "$previous_tag".."$latest_tag" "$@"
 }
 
diff --git a/pre_merge.sh b/pre_merge.sh
index ce038a8d9b..bc67c140d3 100755
--- a/pre_merge.sh
+++ b/pre_merge.sh
@@ -9,7 +9,7 @@ source "$mydir/merge_helpers.sh"
 require_clean_git
 
 # Revert Schildi's upstream string changes
-git checkout `upstream_previous_tag` -- "$mydir/vector/src/main/res/**/strings.xml"
+git checkout `upstream_common_base` -- "$mydir/vector/src/main/res/**/strings.xml"
 git commit -m "Automatic revert to unchanged upstream strings, pt.1"
 
 # Keep in sync with post_merge.sh!