difftool/mergetool: refactor commands to use git-mergetool--lib

This consolidates the common functionality from git-mergetool and
git-difftool--helper into a single git-mergetool--lib scriptlet.

Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/.gitignore b/.gitignore
index a36da9d981e4153b0cd20d0737f958b3da1f4efc..757c7f0ad9461747563cd680877e9a15f96a49e6 100644 (file)
--- a/.gitignore
+++ b/.gitignore
@@ -80,6 +80,7 @@ git-merge-recursive
 git-merge-resolve
 git-merge-subtree
 git-mergetool
+git-mergetool--lib
 git-mktag
 git-mktree
 git-name-rev

diff --git a/Documentation/git-mergetool--lib.txt b/Documentation/git-mergetool--lib.txt
new file mode 100644 (file)
index 0000000..3d57031
--- /dev/null
+++ b/Documentation/git-mergetool--lib.txt
@@ -0,0 +1,56 @@
+git-mergetool--lib(1)
+=====================
+
+NAME
+----
+git-mergetool--lib - Common git merge tool shell scriptlets
+
+SYNOPSIS
+--------
+'. "$(git --exec-path)/git-mergetool--lib"'
+
+DESCRIPTION
+-----------
+
+This is not a command the end user would want to run.  Ever.
+This documentation is meant for people who are studying the
+Porcelain-ish scripts and/or are writing new ones.
+
+The 'git-mergetool--lib' scriptlet is designed to be sourced (using
+`.`) by other shell scripts to set up functions for working
+with git merge tools.
+
+Before sourcing it, your script should set up a few variables;
+`TOOL_MODE` is used to define the operation mode for various
+functions.  'diff' and 'merge' are valid values.
+
+FUNCTIONS
+---------
+get_merge_tool::
+       returns a merge tool
+
+get_merge_tool_cmd::
+       returns the custom command for a merge tool.
+
+get_merge_tool_path::
+       returns the custom path for a merge tool.
+
+run_merge_tool::
+       launches a merge tool given the tool name and a true/false
+       flag to indicate whether a merge base is present.
+       '$merge_tool', '$merge_tool_path', and for custom commands,
+       '$merge_tool_cmd', must be defined prior to calling
+       run_merge_tool.  Additionally, '$MERGED', '$LOCAL', '$REMOTE',
+       and '$BASE' must be defined for use by the merge tool.
+
+Author
+------
+Written by David Aguilar <davvid@gmail.com>
+
+Documentation
+--------------
+Documentation by David Aguilar and the git-list <git@vger.kernel.org>.
+
+GIT
+---
+Part of the linkgit:git[1] suite

diff --git a/Makefile b/Makefile
index a80055f38d8d3e080fffe0164752b5819c0379fa..3e56274d36e9ac83291554c782ac9173741ed166 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -284,6 +284,7 @@ SCRIPT_SH += git-merge-octopus.sh
 SCRIPT_SH += git-merge-one-file.sh
 SCRIPT_SH += git-merge-resolve.sh
 SCRIPT_SH += git-mergetool.sh
+SCRIPT_SH += git-mergetool--lib.sh
 SCRIPT_SH += git-parse-remote.sh
 SCRIPT_SH += git-pull.sh
 SCRIPT_SH += git-quiltimport.sh

diff --git a/git-difftool--helper.sh b/git-difftool--helper.sh
index f3c27d86adf3ba158de4749d45c4ac54e7887e76..b4500368c3268bb26aa22ccf75b9b2fd4bc94df1 100755 (executable)
--- a/git-difftool--helper.sh
+++ b/git-difftool--helper.sh
@@ -5,6 +5,10 @@
 #
 # Copyright (c) 2009 David Aguilar
 
+# Load common functions from git-mergetool--lib
+TOOL_MODE=diff
+. git-mergetool--lib
+
 # difftool.prompt controls the default prompt/no-prompt behavior
 # and is overridden with $GIT_DIFFTOOL*_PROMPT.
 should_prompt () {
@@ -16,8 +20,7 @@ should_prompt () {
        fi
 }
 
-# This function prepares temporary files and launches the appropriate
-# merge tool.
+# Sets up shell variables and runs a merge tool
 launch_merge_tool () {
        # Merged is the filename as it appears in the work tree
        # Local is the contents of a/filename
@@ -37,187 +40,16 @@ launch_merge_tool () {
        fi
 
        # Run the appropriate merge tool command
-       case "$merge_tool" in
-       kdiff3)
-               basename=$(basename "$MERGED")
-               "$merge_tool_path" --auto \
-                       --L1 "$basename (A)" \
-                       --L2 "$basename (B)" \
-                       "$LOCAL" "$REMOTE" \
-                       > /dev/null 2>&1
-               ;;
-
-       kompare)
-               "$merge_tool_path" "$LOCAL" "$REMOTE"
-               ;;
-
-       tkdiff)
-               "$merge_tool_path" "$LOCAL" "$REMOTE"
-               ;;
-
-       meld)
-               "$merge_tool_path" "$LOCAL" "$REMOTE"
-               ;;
-
-       diffuse)
-               "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
-               ;;
-
-       vimdiff)
-               "$merge_tool_path" -d -c "wincmd l" "$LOCAL" "$REMOTE"
-               ;;
-
-       gvimdiff)
-               "$merge_tool_path" -d -c "wincmd l" -f "$LOCAL" "$REMOTE"
-               ;;
-
-       xxdiff)
-               "$merge_tool_path" \
-                       -R 'Accel.Search: "Ctrl+F"' \
-                       -R 'Accel.SearchForward: "Ctrl-G"' \
-                       "$LOCAL" "$REMOTE"
-               ;;
-
-       opendiff)
-               "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
-               ;;
-
-       ecmerge)
-               "$merge_tool_path" "$LOCAL" "$REMOTE" \
-                       --default --mode=merge2 --to="$MERGED"
-               ;;
-
-       emerge)
-               "$merge_tool_path" -f emerge-files-command \
-                       "$LOCAL" "$REMOTE" "$(basename "$MERGED")"
-               ;;
-
-       *)
-               if test -n "$merge_tool_cmd"; then
-                       ( eval $merge_tool_cmd )
-               fi
-               ;;
-       esac
-}
-
-# Verifies that (difftool|mergetool).<tool>.cmd exists
-valid_custom_tool() {
-       merge_tool_cmd="$(git config difftool.$1.cmd)"
-       test -z "$merge_tool_cmd" &&
-       merge_tool_cmd="$(git config mergetool.$1.cmd)"
-       test -n "$merge_tool_cmd"
-}
-
-# Verifies that the chosen merge tool is properly setup.
-# Built-in merge tools are always valid.
-valid_tool() {
-       case "$1" in
-       kdiff3 | kompare | tkdiff | xxdiff | meld | opendiff | emerge | vimdiff | gvimdiff | ecmerge)
-               ;; # happy
-       *)
-               if ! valid_custom_tool "$1"
-               then
-                       return 1
-               fi
-               ;;
-       esac
-}
-
-# Sets up the merge_tool_path variable.
-# This handles the difftool.<tool>.path configuration.
-# This also falls back to mergetool defaults.
-init_merge_tool_path() {
-       merge_tool_path=$(git config difftool."$1".path)
-       test -z "$merge_tool_path" &&
-       merge_tool_path=$(git config mergetool."$1".path)
-       if test -z "$merge_tool_path"; then
-               case "$1" in
-               vimdiff)
-                       merge_tool_path=vim
-                       ;;
-               gvimdiff)
-                       merge_tool_path=gvim
-                       ;;
-               emerge)
-                       merge_tool_path=emacs
-                       ;;
-               *)
-                       merge_tool_path="$1"
-                       ;;
-               esac
-       fi
+       run_merge_tool "$merge_tool"
 }
 
 # Allow GIT_DIFF_TOOL and GIT_MERGE_TOOL to provide default values
 test -n "$GIT_MERGE_TOOL" && merge_tool="$GIT_MERGE_TOOL"
 test -n "$GIT_DIFF_TOOL" && merge_tool="$GIT_DIFF_TOOL"
 
-# If merge tool was not specified then use the diff.tool
-# configuration variable.  If that's invalid then reset merge_tool.
-# Fallback to merge.tool.
-if test -z "$merge_tool"; then
-       merge_tool=$(git config diff.tool)
-       test -z "$merge_tool" &&
-       merge_tool=$(git config merge.tool)
-       if test -n "$merge_tool" && ! valid_tool "$merge_tool"; then
-               echo >&2 "git config option diff.tool set to unknown tool: $merge_tool"
-               echo >&2 "Resetting to default..."
-               unset merge_tool
-       fi
-fi
-
-# Try to guess an appropriate merge tool if no tool has been set.
-if test -z "$merge_tool"; then
-       # We have a $DISPLAY so try some common UNIX merge tools
-       if test -n "$DISPLAY"; then
-               # If gnome then prefer meld, otherwise, prefer kdiff3 or kompare
-               if test -n "$GNOME_DESKTOP_SESSION_ID" ; then
-                       merge_tool_candidates="meld kdiff3 kompare tkdiff xxdiff gvimdiff diffuse"
-               else
-                       merge_tool_candidates="kdiff3 kompare tkdiff xxdiff meld gvimdiff diffuse"
-               fi
-       fi
-       if echo "${VISUAL:-$EDITOR}" | grep 'emacs' > /dev/null 2>&1; then
-               # $EDITOR is emacs so add emerge as a candidate
-               merge_tool_candidates="$merge_tool_candidates emerge opendiff vimdiff"
-       elif echo "${VISUAL:-$EDITOR}" | grep 'vim' > /dev/null 2>&1; then
-               # $EDITOR is vim so add vimdiff as a candidate
-               merge_tool_candidates="$merge_tool_candidates vimdiff opendiff emerge"
-       else
-               merge_tool_candidates="$merge_tool_candidates opendiff emerge vimdiff"
-       fi
-       echo "merge tool candidates: $merge_tool_candidates"
-
-       # Loop over each candidate and stop when a valid merge tool is found.
-       for i in $merge_tool_candidates
-       do
-               init_merge_tool_path $i
-               if type "$merge_tool_path" > /dev/null 2>&1; then
-                       merge_tool=$i
-                       break
-               fi
-       done
-
-       if test -z "$merge_tool" ; then
-               echo "No known merge resolution program available."
-               exit 1
-       fi
-
-else
-       # A merge tool has been set, so verify that it's valid.
-       if ! valid_tool "$merge_tool"; then
-               echo >&2 "Unknown merge tool $merge_tool"
-               exit 1
-       fi
-
-       init_merge_tool_path "$merge_tool"
-
-       if test -z "$merge_tool_cmd" && ! type "$merge_tool_path" > /dev/null 2>&1; then
-               echo "The merge tool $merge_tool is not available as '$merge_tool_path'"
-               exit 1
-       fi
-fi
-
+merge_tool=$(get_merge_tool "$merge_tool") || exit
+merge_tool_cmd="$(get_merge_tool_cmd "$merge_tool")"
+merge_tool_path="$(get_merge_tool_path "$merge_tool")" || exit
 
 # Launch the merge tool on each path provided by 'git diff'
 while test $# -gt 6

diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
new file mode 100644 (file)
index 0000000..c5db24e
--- /dev/null
+++ b/git-mergetool--lib.sh
@@ -0,0 +1,378 @@
+# git-mergetool--lib is a library for common merge tool functions
+diff_mode() {
+       test "$TOOL_MODE" = diff
+}
+
+merge_mode() {
+       test "$TOOL_MODE" = merge
+}
+
+translate_merge_tool_path () {
+       if test -n "$2"; then
+               echo "$2"
+       else
+               case "$1" in
+               vimdiff)
+                       path=vim
+                       ;;
+               gvimdiff)
+                       path=gvim
+                       ;;
+               emerge)
+                       path=emacs
+                       ;;
+               *)
+                       path="$1"
+                       ;;
+               esac
+               echo "$path"
+       fi
+}
+
+check_unchanged () {
+       if test "$MERGED" -nt "$BACKUP"; then
+               status=0
+       else
+               while true; do
+                       echo "$MERGED seems unchanged."
+                       printf "Was the merge successful? [y/n] "
+                       read answer < /dev/tty
+                       case "$answer" in
+                       y*|Y*) status=0; break ;;
+                       n*|N*) status=1; break ;;
+                       esac
+               done
+       fi
+}
+
+valid_tool () {
+       case "$1" in
+       kdiff3 | tkdiff | xxdiff | meld | opendiff | \
+       emerge | vimdiff | gvimdiff | ecmerge | diffuse)
+               ;; # happy
+       tortoisemerge)
+               if ! merge_mode; then
+                       return 1
+               fi
+               ;;
+       kompare)
+               if ! diff_mode; then
+                       return 1
+               fi
+               ;;
+       *)
+               if test -z "$(get_merge_tool_cmd "$1")"; then
+                       return 1
+               fi
+               ;;
+       esac
+}
+
+get_merge_tool_cmd () {
+       diff_mode &&
+       custom_cmd="$(git config difftool.$1.cmd)"
+       test -z "$custom_cmd" &&
+       custom_cmd="$(git config mergetool.$1.cmd)"
+       test -n "$custom_cmd" &&
+       echo "$custom_cmd"
+}
+
+run_merge_tool () {
+       base_present="$2"
+       status=0
+
+       case "$1" in
+       kdiff3)
+               if merge_mode; then
+                       if $base_present; then
+                               ("$merge_tool_path" --auto \
+                                       --L1 "$MERGED (Base)" \
+                                       --L2 "$MERGED (Local)" \
+                                       --L3 "$MERGED (Remote)" \
+                                       -o "$MERGED" \
+                                       "$BASE" "$LOCAL" "$REMOTE" \
+                               > /dev/null 2>&1)
+                       else
+                               ("$merge_tool_path" --auto \
+                                       --L1 "$MERGED (Local)" \
+                                       --L2 "$MERGED (Remote)" \
+                                       -o "$MERGED" \
+                                       "$LOCAL" "$REMOTE" \
+                               > /dev/null 2>&1)
+                       fi
+                       status=$?
+               else
+                       ("$merge_tool_path" --auto \
+                        --L1 "$MERGED (A)" \
+                        --L2 "$MERGED (B)" "$LOCAL" "$REMOTE" \
+                        > /dev/null 2>&1)
+               fi
+               ;;
+       kompare)
+               "$merge_tool_path" "$LOCAL" "$REMOTE"
+               ;;
+       tkdiff)
+               if merge_mode; then
+                       if $base_present; then
+                               "$merge_tool_path" -a "$BASE" \
+                                       -o "$MERGED" "$LOCAL" "$REMOTE"
+                       else
+                               "$merge_tool_path" \
+                                       -o "$MERGED" "$LOCAL" "$REMOTE"
+                       fi
+                       status=$?
+               else
+                       "$merge_tool_path" "$LOCAL" "$REMOTE"
+               fi
+               ;;
+       meld)
+               if merge_mode; then
+                       touch "$BACKUP"
+                       "$merge_tool_path" "$LOCAL" "$MERGED" "$REMOTE"
+                       check_unchanged
+               else
+                       "$merge_tool_path" "$LOCAL" "$REMOTE"
+               fi
+               ;;
+       diffuse)
+               if merge_mode; then
+                       touch "$BACKUP"
+                       if $base_present; then
+                               "$merge_tool_path" \
+                                       "$LOCAL" "$MERGED" "$REMOTE" \
+                                       "$BASE" | cat
+                       else
+                               "$merge_tool_path" \
+                                       "$LOCAL" "$MERGED" "$REMOTE" | cat
+                       fi
+                       check_unchanged
+               else
+                       "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
+               fi
+               ;;
+       vimdiff)
+               if merge_mode; then
+                       touch "$BACKUP"
+                       "$merge_tool_path" -d -c "wincmd l" \
+                               "$LOCAL" "$MERGED" "$REMOTE"
+                       check_unchanged
+               else
+                       "$merge_tool_path" -d -c "wincmd l" \
+                               "$LOCAL" "$REMOTE"
+               fi
+               ;;
+       gvimdiff)
+               if merge_mode; then
+                       touch "$BACKUP"
+                       "$merge_tool_path" -d -c "wincmd l" -f \
+                               "$LOCAL" "$MERGED" "$REMOTE"
+                       check_unchanged
+               else
+                       "$merge_tool_path" -d -c "wincmd l" -f \
+                               "$LOCAL" "$REMOTE"
+               fi
+               ;;
+       xxdiff)
+               if merge_mode; then
+                       touch "$BACKUP"
+                       if $base_present; then
+                               "$merge_tool_path" -X --show-merged-pane \
+                                       -R 'Accel.SaveAsMerged: "Ctrl-S"' \
+                                       -R 'Accel.Search: "Ctrl+F"' \
+                                       -R 'Accel.SearchForward: "Ctrl-G"' \
+                                       --merged-file "$MERGED" \
+                                       "$LOCAL" "$BASE" "$REMOTE"
+                       else
+                               "$merge_tool_path" -X $extra \
+                                       -R 'Accel.SaveAsMerged: "Ctrl-S"' \
+                                       -R 'Accel.Search: "Ctrl+F"' \
+                                       -R 'Accel.SearchForward: "Ctrl-G"' \
+                                       --merged-file "$MERGED" \
+                                       "$LOCAL" "$REMOTE"
+                       fi
+                       check_unchanged
+               else
+                       "$merge_tool_path" \
+                               -R 'Accel.Search: "Ctrl+F"' \
+                               -R 'Accel.SearchForward: "Ctrl-G"' \
+                               "$LOCAL" "$REMOTE"
+               fi
+               ;;
+       opendiff)
+               if merge_mode; then
+                       touch "$BACKUP"
+                       if $base_present; then
+                               "$merge_tool_path" "$LOCAL" "$REMOTE" \
+                                       -ancestor "$BASE" \
+                                       -merge "$MERGED" | cat
+                       else
+                               "$merge_tool_path" "$LOCAL" "$REMOTE" \
+                                       -merge "$MERGED" | cat
+                       fi
+                       check_unchanged
+               else
+                       "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
+               fi
+               ;;
+       ecmerge)
+               if merge_mode; then
+                       touch "$BACKUP"
+                       if $base_present; then
+                               "$merge_tool_path" "$BASE" "$LOCAL" "$REMOTE" \
+                                       --default --mode=merge3 --to="$MERGED"
+                       else
+                               "$merge_tool_path" "$LOCAL" "$REMOTE" \
+                                       --default --mode=merge2 --to="$MERGED"
+                       fi
+                       check_unchanged
+               else
+                       "$merge_tool_path" "$LOCAL" "$REMOTE" \
+                               --default --mode=merge2 --to="$MERGED"
+               fi
+               ;;
+       emerge)
+               if merge_mode; then
+                       if $base_present; then
+                               "$merge_tool_path" \
+                                       -f emerge-files-with-ancestor-command \
+                                       "$LOCAL" "$REMOTE" "$BASE" \
+                                       "$(basename "$MERGED")"
+                       else
+                               "$merge_tool_path" \
+                                       -f emerge-files-command \
+                                       "$LOCAL" "$REMOTE" \
+                                       "$(basename "$MERGED")"
+                       fi
+                       status=$?
+               else
+                       "$merge_tool_path" -f emerge-files-command \
+                               "$LOCAL" "$REMOTE" "$(basename "$MERGED")"
+               fi
+               ;;
+       tortoisemerge)
+               if $base_present; then
+                       touch "$BACKUP"
+                       "$merge_tool_path" \
+                               -base:"$BASE" -mine:"$LOCAL" \
+                               -theirs:"$REMOTE" -merged:"$MERGED"
+                       check_unchanged
+               else
+                       echo "TortoiseMerge cannot be used without a base" 1>&2
+                       status=1
+               fi
+               ;;
+       *)
+               if test -z "$merge_tool_cmd"; then
+                       if merge_mode; then
+                               status=1
+                       fi
+                       break
+               fi
+               if merge_mode; then
+                       if test "$merge_tool_trust_exit_code" = "false"; then
+                               touch "$BACKUP"
+                               ( eval $merge_tool_cmd )
+                               check_unchanged
+                       else
+                               ( eval $merge_tool_cmd )
+                               status=$?
+                       fi
+               else
+                       ( eval $merge_tool_cmd )
+               fi
+               ;;
+       esac
+       return $status
+}
+
+guess_merge_tool () {
+       if merge_mode; then
+               tools="tortoisemerge"
+       else
+               tools="kompare"
+       fi
+       if test -n "$DISPLAY"; then
+               if test -n "$GNOME_DESKTOP_SESSION_ID" ; then
+                       tools="meld opendiff kdiff3 tkdiff xxdiff $tools"
+               else
+                       tools="opendiff kdiff3 tkdiff xxdiff meld $tools"
+               fi
+               tools="$tools gvimdiff diffuse ecmerge"
+       fi
+       if echo "${VISUAL:-$EDITOR}" | grep emacs > /dev/null 2>&1; then
+               # $EDITOR is emacs so add emerge as a candidate
+               tools="$tools emerge vimdiff"
+       elif echo "${VISUAL:-$EDITOR}" | grep vim > /dev/null 2>&1; then
+               # $EDITOR is vim so add vimdiff as a candidate
+               tools="$tools vimdiff emerge"
+       else
+               tools="$tools emerge vimdiff"
+       fi
+       echo >&2 "merge tool candidates: $tools"
+
+       # Loop over each candidate and stop when a valid merge tool is found.
+       for i in $tools
+       do
+               merge_tool_path="$(translate_merge_tool_path "$i")"
+               if type "$merge_tool_path" > /dev/null 2>&1; then
+                       merge_tool="$i"
+                       break
+               fi
+       done
+
+       if test -z "$merge_tool" ; then
+               echo >&2 "No known merge resolution program available."
+               return 1
+       fi
+       echo "$merge_tool"
+}
+
+get_configured_merge_tool () {
+       # Diff mode first tries diff.tool and falls back to merge.tool.
+       # Merge mode only checks merge.tool
+       if diff_mode; then
+               tool=$(git config diff.tool)
+       fi
+       if test -z "$tool"; then
+               tool=$(git config merge.tool)
+       fi
+       if test -n "$merge_tool" && ! valid_tool "$merge_tool"; then
+               echo >&2 "git config option $TOOL_MODE.tool set to unknown tool: $merge_tool"
+               echo >&2 "Resetting to default..."
+               return 1
+       fi
+       echo "$tool"
+}
+
+get_merge_tool_path () {
+       # A merge tool has been set, so verify that it's valid.
+       if ! valid_tool "$merge_tool"; then
+               echo >&2 "Unknown merge tool $merge_tool"
+               exit 1
+       fi
+       if diff_mode; then
+               merge_tool_path=$(git config difftool."$merge_tool".path)
+       fi
+       if test -z "$merge_tool_path"; then
+               merge_tool_path=$(git config mergetool."$merge_tool".path)
+       fi
+       merge_tool_path="$(translate_merge_tool_path "$merge_tool" "$merge_tool_path")"
+       if test -z "$merge_tool_cmd" && ! type "$merge_tool_path" > /dev/null 2>&1; then
+               echo >&2 "The $TOOL_MODE tool $merge_tool is not available as '$merge_tool_path'"
+               exit 1
+       fi
+       echo "$merge_tool_path"
+}
+
+get_merge_tool () {
+       merge_tool="$1"
+       # Check if a merge tool has been configured
+       if test -z "$merge_tool"; then
+               merge_tool=$(get_configured_merge_tool)
+       fi
+       # Try to guess an appropriate merge tool if no tool has been set.
+       if test -z "$merge_tool"; then
+               merge_tool=$(guess_merge_tool) || exit
+       fi
+       echo "$merge_tool"
+}

diff --git a/git-mergetool.sh b/git-mergetool.sh
index cceebb72103033927a520415203a23f89fa0c5d0..efa31a228ebbb07259132e2702b91e6623e1db5f 100755 (executable)
--- a/git-mergetool.sh
+++ b/git-mergetool.sh
@@ -11,7 +11,9 @@
 USAGE='[--tool=tool] [-y|--no-prompt|--prompt] [file to merge] ...'
 SUBDIRECTORY_OK=Yes
 OPTIONS_SPEC=
+TOOL_MODE=merge
 . git-sh-setup
+. git-mergetool--lib
 require_work_tree
 
 # Returns true if the mode reflects a symlink
@@ -110,22 +112,6 @@ resolve_deleted_merge () {
        done
 }
 
-check_unchanged () {
-    if test "$MERGED" -nt "$BACKUP" ; then
-       status=0;
-    else
-       while true; do
-           echo "$MERGED seems unchanged."
-           printf "Was the merge successful? [y/n] "
-           read answer < /dev/tty
-           case "$answer" in
-               y*|Y*) status=0; break ;;
-               n*|N*) status=1; break ;;
-           esac
-       done
-    fi
-}
-
 checkout_staged_file () {
     tmpfile=$(expr "$(git checkout-index --temp --stage="$1" "$2")" : '\([^    ]*\)    ')
 
@@ -188,107 +174,11 @@ merge_file () {
        read ans
     fi
 
-    case "$merge_tool" in
-       kdiff3)
-           if base_present ; then
-               ("$merge_tool_path" --auto --L1 "$MERGED (Base)" --L2 "$MERGED (Local)" --L3 "$MERGED (Remote)" \
-                   -o "$MERGED" "$BASE" "$LOCAL" "$REMOTE" > /dev/null 2>&1)
-           else
-               ("$merge_tool_path" --auto --L1 "$MERGED (Local)" --L2 "$MERGED (Remote)" \
-                   -o "$MERGED" "$LOCAL" "$REMOTE" > /dev/null 2>&1)
-           fi
-           status=$?
-           ;;
-       tkdiff)
-           if base_present ; then
-               "$merge_tool_path" -a "$BASE" -o "$MERGED" "$LOCAL" "$REMOTE"
-           else
-               "$merge_tool_path" -o "$MERGED" "$LOCAL" "$REMOTE"
-           fi
-           status=$?
-           ;;
-       meld)
-           touch "$BACKUP"
-           "$merge_tool_path" "$LOCAL" "$MERGED" "$REMOTE"
-           check_unchanged
-           ;;
-       vimdiff)
-           touch "$BACKUP"
-           "$merge_tool_path" -d -c "wincmd l" "$LOCAL" "$MERGED" "$REMOTE"
-           check_unchanged
-           ;;
-       gvimdiff)
-           touch "$BACKUP"
-           "$merge_tool_path" -d -c "wincmd l" -f "$LOCAL" "$MERGED" "$REMOTE"
-           check_unchanged
-           ;;
-       xxdiff)
-           touch "$BACKUP"
-           if base_present ; then
-               "$merge_tool_path" -X --show-merged-pane \
-                   -R 'Accel.SaveAsMerged: "Ctrl-S"' \
-                   -R 'Accel.Search: "Ctrl+F"' \
-                   -R 'Accel.SearchForward: "Ctrl-G"' \
-                   --merged-file "$MERGED" "$LOCAL" "$BASE" "$REMOTE"
-           else
-               "$merge_tool_path" -X --show-merged-pane \
-                   -R 'Accel.SaveAsMerged: "Ctrl-S"' \
-                   -R 'Accel.Search: "Ctrl+F"' \
-                   -R 'Accel.SearchForward: "Ctrl-G"' \
-                   --merged-file "$MERGED" "$LOCAL" "$REMOTE"
-           fi
-           check_unchanged
-           ;;
-       opendiff)
-           touch "$BACKUP"
-           if base_present; then
-               "$merge_tool_path" "$LOCAL" "$REMOTE" -ancestor "$BASE" -merge "$MERGED" | cat
-           else
-               "$merge_tool_path" "$LOCAL" "$REMOTE" -merge "$MERGED" | cat
-           fi
-           check_unchanged
-           ;;
-       ecmerge)
-           touch "$BACKUP"
-           if base_present; then
-               "$merge_tool_path" "$BASE" "$LOCAL" "$REMOTE" --default --mode=merge3 --to="$MERGED"
-           else
-               "$merge_tool_path" "$LOCAL" "$REMOTE" --default --mode=merge2 --to="$MERGED"
-           fi
-           check_unchanged
-           ;;
-       emerge)
-           if base_present ; then
-               "$merge_tool_path" -f emerge-files-with-ancestor-command "$LOCAL" "$REMOTE" "$BASE" "$(basename "$MERGED")"
-           else
-               "$merge_tool_path" -f emerge-files-command "$LOCAL" "$REMOTE" "$(basename "$MERGED")"
-           fi
-           status=$?
-           ;;
-       tortoisemerge)
-           if base_present ; then
-               touch "$BACKUP"
-               "$merge_tool_path" -base:"$BASE" -mine:"$LOCAL" -theirs:"$REMOTE" -merged:"$MERGED"
-               check_unchanged
-           else
-               echo "TortoiseMerge cannot be used without a base" 1>&2
-               status=1
-           fi
-           ;;
-       *)
-           if test -n "$merge_tool_cmd"; then
-               if test "$merge_tool_trust_exit_code" = "false"; then
-                   touch "$BACKUP"
-                   ( eval $merge_tool_cmd )
-                   check_unchanged
-               else
-                   ( eval $merge_tool_cmd )
-                   status=$?
-               fi
-           fi
-           ;;
-    esac
-    if test "$status" -ne 0; then
+    present=false
+    base_present &&
+    present=true
+
+    if ! run_merge_tool "$merge_tool" "$present"; then
        echo "merge of $MERGED failed" 1>&2
        mv -- "$BACKUP" "$MERGED"
 
@@ -347,44 +237,6 @@ do
     shift
 done
 
-valid_custom_tool()
-{
-    merge_tool_cmd="$(git config mergetool.$1.cmd)"
-    test -n "$merge_tool_cmd"
-}
-
-valid_tool() {
-       case "$1" in
-               kdiff3 | tkdiff | xxdiff | meld | opendiff | emerge | vimdiff | gvimdiff | ecmerge | tortoisemerge)
-                       ;; # happy
-               *)
-                       if ! valid_custom_tool "$1"; then
-                               return 1
-                       fi
-                       ;;
-       esac
-}
-
-init_merge_tool_path() {
-       merge_tool_path=$(git config mergetool.$1.path)
-       if test -z "$merge_tool_path" ; then
-               case "$1" in
-                       vimdiff)
-                               merge_tool_path=vim
-                               ;;
-                       gvimdiff)
-                               merge_tool_path=gvim
-                               ;;
-                       emerge)
-                               merge_tool_path=emacs
-                               ;;
-                       *)
-                               merge_tool_path=$1
-                               ;;
-               esac
-       fi
-}
-
 prompt_after_failed_merge() {
     while true; do
        printf "Continue merging other unresolved paths (y/n) ? "
@@ -402,62 +254,12 @@ prompt_after_failed_merge() {
     done
 }
 
-if test -z "$merge_tool"; then
-    merge_tool=$(git config merge.tool)
-    if test -n "$merge_tool" && ! valid_tool "$merge_tool"; then
-           echo >&2 "git config option merge.tool set to unknown tool: $merge_tool"
-           echo >&2 "Resetting to default..."
-           unset merge_tool
-    fi
-fi
-
-if test -z "$merge_tool" ; then
-    if test -n "$DISPLAY"; then
-        if test -n "$GNOME_DESKTOP_SESSION_ID" ; then
-            merge_tool_candidates="meld kdiff3 tkdiff xxdiff tortoisemerge gvimdiff diffuse"
-        else
-            merge_tool_candidates="kdiff3 tkdiff xxdiff meld tortoisemerge gvimdiff diffuse"
-        fi
-    fi
-    if echo "${VISUAL:-$EDITOR}" | grep 'emacs' > /dev/null 2>&1; then
-        merge_tool_candidates="$merge_tool_candidates emerge opendiff vimdiff"
-    elif echo "${VISUAL:-$EDITOR}" | grep 'vim' > /dev/null 2>&1; then
-        merge_tool_candidates="$merge_tool_candidates vimdiff opendiff emerge"
-    else
-        merge_tool_candidates="$merge_tool_candidates opendiff emerge vimdiff"
-    fi
-    echo "merge tool candidates: $merge_tool_candidates"
-    for i in $merge_tool_candidates; do
-        init_merge_tool_path $i
-        if type "$merge_tool_path" > /dev/null 2>&1; then
-            merge_tool=$i
-            break
-        fi
-    done
-    if test -z "$merge_tool" ; then
-       echo "No known merge resolution program available."
-       exit 1
-    fi
-else
-    if ! valid_tool "$merge_tool"; then
-        echo >&2 "Unknown merge_tool $merge_tool"
-        exit 1
-    fi
-
-    init_merge_tool_path "$merge_tool"
-
-    merge_keep_backup="$(git config --bool merge.keepBackup || echo true)"
-    merge_keep_temporaries="$(git config --bool mergetool.keepTemporaries || echo false)"
-
-    if test -z "$merge_tool_cmd" && ! type "$merge_tool_path" > /dev/null 2>&1; then
-        echo "The merge tool $merge_tool is not available as '$merge_tool_path'"
-        exit 1
-    fi
-
-    if ! test -z "$merge_tool_cmd"; then
-        merge_tool_trust_exit_code="$(git config --bool mergetool.$merge_tool.trustExitCode || echo false)"
-    fi
-fi
+merge_tool=$(get_merge_tool "$merge_tool") || exit
+merge_tool_cmd="$(get_merge_tool_cmd "$merge_tool")"
+merge_tool_path="$(get_merge_tool_path "$merge_tool")" || exit
+merge_keep_backup="$(git config --bool merge.keepBackup || echo true)"
+merge_keep_temporaries="$(git config --bool mergetool.keepTemporaries || echo false)"
+merge_tool_trust_exit_code="$(git config --bool mergetool."$merge_tool".trustExitCode || echo false)"
 
 last_status=0
 rollup_status=0