From d343300625927dc5c2ed1ed0d13eeef8388ad681 Mon Sep 17 00:00:00 2001
From: carlfriedrich <carlfriedrich@posteo.de>
Date: Fri, 22 Jul 2022 14:41:38 +0200
Subject: [PATCH] grb: rebase on parent of the selected commit

The git rebase command needs to be passed the parent commit of the one
you want to edit. When selecting a commit interactively via fzf, it
makes sense to automatically pass the parent commit of the selected one.
Within fzf it's otherwise quite hard to find the parent commit by hand
if you have found your commit via an fzf search string.
---
 conf.d/forgit.plugin.fish | 12 +++++++++---
 forgit.plugin.zsh         | 14 +++++++++++---
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/conf.d/forgit.plugin.fish b/conf.d/forgit.plugin.fish
index 4a98d02..ab4dda4 100644
--- a/conf.d/forgit.plugin.fish
+++ b/conf.d/forgit.plugin.fish
@@ -437,10 +437,16 @@ function forgit::rebase -d "git rebase"
         --preview=\"$preview\"
         $FORGIT_REBASE_FZF_OPTS
     "
-    set commit (eval "$cmd" | FZF_DEFAULT_OPTS="$opts" fzf | eval "$forgit_extract_sha")
+    set target_commit (eval "$cmd" | FZF_DEFAULT_OPTS="$opts" fzf | eval "$forgit_extract_sha")
 
-    if test $commit
-        git rebase -i "$commit"
+    if test $target_commit
+        # "$target_commit~" is invalid when the commit is the first commit, but we can use "--root" instead
+        set prev_commit "$target_commit~"
+        if test "(git rev-parse '$target_commit')" = "(git rev-list --max-parents=0 HEAD)"
+            set prev_commit "--root"
+        end
+
+        git rebase -i "$prev_commit"
     end
 end
 
diff --git a/forgit.plugin.zsh b/forgit.plugin.zsh
index 55556fa..606c23b 100755
--- a/forgit.plugin.zsh
+++ b/forgit.plugin.zsh
@@ -177,7 +177,7 @@ forgit::cherry::pick() {
 
 forgit::rebase() {
     forgit::inside_work_tree || return 1
-    local cmd preview opts graph files commit
+    local cmd preview opts graph files target_commit prev_commit
     graph=--graph
     [[ $FORGIT_LOG_GRAPH_ENABLE == false ]] && graph=
     cmd="git log $graph --color=always --format='$forgit_log_format' $* $forgit_emojify"
@@ -190,8 +190,16 @@ forgit::rebase() {
         --preview=\"$preview\"
         $FORGIT_REBASE_FZF_OPTS
     "
-    commit=$(eval "$cmd" | FZF_DEFAULT_OPTS="$opts" fzf | eval "$forgit_extract_sha")
-    [[ -n "$commit" ]] && git rebase -i "$commit"
+    target_commit=$(eval "$cmd" | FZF_DEFAULT_OPTS="$opts" fzf | eval "$forgit_extract_sha")
+    if [[ -n "$target_commit" ]]; then
+        # "$target_commit~" is invalid when the commit is the first commit, but we can use "--root" instead
+        if [[ "$(git rev-parse "$target_commit")" == "$(git rev-list --max-parents=0 HEAD)" ]]; then
+            prev_commit="--root"
+        else
+            prev_commit="$target_commit~"
+        fi
+        git rebase -i "$prev_commit"
+    fi
 }
 
 forgit::fixup() {