Re: re-running merge on a single file

[Chris Packham <judge.packham@gmail.com>]

On Thu, Mar 11, 2010 at 10:56 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Johannes Sixt <j.sixt@viscovery.net> writes:
>
>> Chris Packham schrieb:
>>> $ git checkout --merge -- cpu/mpc83xx/start.S
>>> $ git show :1:$(git rev-parse --show-prefix)cpu/mpc83xx/start.S
>>> fatal: Path 'cpu/mpc83xx/start.S' is in the index, but not at stage 1.
>>> Did you mean ':0:cpu/mpc83xx/start.S'?
>>
>> Both of these work only as long as the index still records the conflicted
>> state. If you (or one of your tools) has git-added the file, or you have
>> git-checked-out some version of the file, the conflict stages are lost,
>> and you must reset --hard and redo the entire merge.
>
> If the merge textually autoresolves cleanly, you might not even have any
> conflicted state to begin with.  In such a case you would need to grab
>
>        MERGE_HEAD:path-to-that-thing
>        HEAD:path-to-that-thing
>
> yourself.
>

So if I understand correctly once I've committed the merge the various
stages and MERGE_HEADs go away. I don't really want to re-do the whole
merge which is probably the correct thing to do. I'm lazy and my
projects rules allow broken commits so instead I can poke about with
git show and various revisions.

Here's a simple script that does just that. I've borrowed some command
line options from git mergetool (Warning: gmail web interface). If
anyone is interested in seeing a proper version of this I can clean it
up submit it properly.

----8<----

From c6ad177712422cbba641975d9e6a5fe85fc8f1fa Mon Sep 17 00:00:00 2001
From: Chris Packham <judge.packham@gmail.com>
Date: Fri, 12 Mar 2010 12:03:02 -0800
Subject: [PATCH] Add git manual-merge command

Can be used to manually merge files from the specified revisions.
---
 git-manual-merge |   91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 91 insertions(+), 0 deletions(-)
 create mode 100755 git-manual-merge

diff --git a/git-manual-merge b/git-manual-merge
new file mode 100755
index 0000000..f37ba88
--- /dev/null
+++ b/git-manual-merge
@@ -0,0 +1,91 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Chris Packham
+#
+# Based on git-mergetool by Theodore Y. Ts'o
+#
+# This file is licensed under the GPL v2
+#
+
+USAGE='<branch1> <branch2> <file> ...'
+. git-sh-setup
+. git-mergetool--lib
+require_work_tree
+
+merge_one_file()
+{
+    local has_base=false
+    git show $1:$4 > $4.$1 && has_base=true
+    git show $2:$4 > $4.$2 || die
+    git show $3:$4 > $4.$3 || die
+
+    if "$prompt" = true; then
+       printf "Hit return to start merge resolution tool (%s): " "$merge_tool"
+       read ans
+    fi
+
+    if "$has_base" = true; then
+        $merge_tool $4.$1 $4.$2 $4.$1 -o $4
+    else
+        $merge_tool $4.$2 $4.$1 -o $4
+    fi
+}
+
+prompt=$(git config --bool mergetool.prompt || echo true)
+
+while test $# != 0
+do
+    case "$1" in
+        -t|--tool*)
+            case "$#,$1" in
+                *,*=*)
+                    merge_tool=$(expr "z$1" : 'z-[^=]*=\(.*\)')
+                    ;;
+                1,*)
+                    usage ;;
+                *)
+                    merge_tool="$2"
+                    shift ;;
+            esac
+            ;;
+        -y|--no-prompt)
+            prompt=false
+            ;;
+        --prompt)
+            prompt=true
+            ;;
+        --)
+            shift
+            break
+            ;;
+        -*)
+            usage
+            ;;
+        *)
+            break
+            ;;
+    esac
+    shift
+done
+
+echo "$merge_tool"
+
+if test $# -lt 3; then
+    usage
+fi
+
+branch1=$(git rev-parse --short  $1)
+branch2=$(git rev-parse --short  $2)
+_base=$(git merge-base $branch1 $branch2)
+base=$(git rev-parse --short  $_base)
+
+if test -z "$merge_tool"; then
+    merge_tool=$(get_merge_tool "$merge_tool") || exit
+fi
+
+shift 2
+
+for x in $*; do
+    merge_one_file $base $branch1 $branch2 $x
+done
+
--
1.7.0.1