[PATCH v9] Support auto-merge for meld to follow the vim-diff behavior

From: sunlin via GitGitGadget <gitgitgadget@gmail.com>
Date: Jul 6, 2020, 02:27 UTC
Message-ID: <pull.781.v9.git.git.1594002423685.gitgitgadget@gmail.com>
In-Reply-To: <pull.781.v8.git.git.1593825400699.gitgitgadget@gmail.com>

From: Lin Sun <lin.sun@zoom.us>

Make the mergetool used with "meld" backend behave similarly to "vimdiff" by telling it to auto-merge non-conflicting parts and highlight the conflicting parts when `mergetool.meld.useAutoMerge` is configured with `true`, or `auto` for detecting the `--auto-merge` option automatically.

Helped-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Lin Sun <lin.sun@zoom.us>
---
    Enable auto-merge for meld to follow the vimdiff beharior
    
    Hi, the mergetool "meld" does NOT merge the no-conflict changes, while
    the mergetool "vimdiff" will merge the no-conflict changes and highlight
    the conflict parts. This patch will make the mergetool "meld" similar to
    "vimdiff", auto-merge the no-conflict changes, highlight conflict parts.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-781%2Fsunlin7%2Fmaster-v9
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-781/sunlin7/master-v9
Pull-Request: https://github.com/git/git/pull/781

Range-diff vs v8:

 1:  f28a32c66e ! 1:  95586fb2c2 Support auto-merge for meld to follow the vim-diff behavior
     @@ mergetools/meld: diff_cmd () {
      -	else
      -		meld_has_output_option=false
      +		meld_use_auto_merge_option=$(git config mergetool.meld.useAutoMerge)
     -+		if test -z "$meld_use_auto_merge_option"
     -+		then
     ++		case "$meld_use_auto_merge_option" in
     ++		"")
      +			meld_use_auto_merge_option=false
     -+		else
     ++			;;
     ++		[Aa]uto)
     ++			# testing the "--auto-merge" option only if config is "[Aa]uto"
     ++			init_meld_help_msg
     ++
     ++			case "$meld_help_msg" in
     ++			*"--auto-merge"*)
     ++				meld_use_auto_merge_option=true
     ++				;;
     ++			*)
     ++				meld_use_auto_merge_option=false
     ++				;;
     ++			esac
     ++			;;
     ++		*)
      +			bool_value=$(git config --bool mergetool.meld.useAutoMerge 2>/dev/null)
      +			if test -n "$bool_value"
      +			then
      +				meld_use_auto_merge_option="$bool_value"
     -+			elif test "$meld_use_auto_merge_option" = "auto" \
     -+				|| test "$meld_use_auto_merge_option" = "Auto"
     -+			then
     -+				# testing the "--auto-merge" option only if config is "[Aa]uto"
     -+				init_meld_help_msg
     -+
     -+				case "$meld_help_msg" in
     -+				*"--auto-merge"*)
     -+					meld_use_auto_merge_option=true
     -+					;;
     -+				*)
     -+					meld_use_auto_merge_option=false
     -+					;;
     -+				esac
      +			else
      +				meld_use_auto_merge_option=false
      +			fi
     -+		fi
     ++			;;
     ++		esac
       	fi
       }

 Documentation/config/mergetool.txt | 10 ++++
 mergetools/meld                    | 86 ++++++++++++++++++++++++------
 2 files changed, 80 insertions(+), 16 deletions(-)

diff --git a/Documentation/config/mergetool.txt b/Documentation/config/mergetool.txt
index 09ed31dbfa..031c78aa95 100644
--- a/Documentation/config/mergetool.txt
+++ b/Documentation/config/mergetool.txt
@@ -30,6 +30,16 @@ mergetool.meld.hasOutput::
 	to `true` tells Git to unconditionally use the `--output` option,
 	and `false` avoids using `--output`.
 
+mergetool.meld.useAutoMerge::
+	When the `--auto-merge` is given, meld will merge all non-conflicting
+	parts automatically, highlight the conflicting parts and waiting for
+	user decision.  Setting `mergetool.meld.useAutoMerge` to `true` tells
+	Git to unconditionally use the `--auto-merge` option with `meld`.
+	Setting this value to `auto` makes git detect whether `--auto-merge`
+	is supported and will only use `--auto-merge` when available.  A
+	value of `false` avoids using `--auto-merge` altogether, and is the
+	default value.
+
 mergetool.keepBackup::
 	After performing a merge, the original file with conflict markers
 	can be saved as a file with a `.orig` extension.  If this variable
diff --git a/mergetools/meld b/mergetools/meld
index 7a08470f88..ba6607a088 100644
--- a/mergetools/meld
+++ b/mergetools/meld
@@ -3,34 +3,88 @@ diff_cmd () {
 }
 
 merge_cmd () {
-	if test -z "${meld_has_output_option:+set}"
+	check_meld_for_features
+
+	option_auto_merge=
+	if test "$meld_use_auto_merge_option" = true
 	then
-		check_meld_for_output_version
+		option_auto_merge="--auto-merge"
 	fi
 
 	if test "$meld_has_output_option" = true
 	then
-		"$merge_tool_path" --output="$MERGED" \
+		"$merge_tool_path" $option_auto_merge --output="$MERGED" \
 			"$LOCAL" "$BASE" "$REMOTE"
 	else
-		"$merge_tool_path" "$LOCAL" "$MERGED" "$REMOTE"
+		"$merge_tool_path" $option_auto_merge "$LOCAL" "$MERGED" "$REMOTE"
 	fi
 }
 
-# Check whether we should use 'meld --output <file>'
-check_meld_for_output_version () {
-	meld_path="$(git config mergetool.meld.path)"
-	meld_path="${meld_path:-meld}"
+# Get meld help message
+init_meld_help_msg () {
+	if test -z "$meld_help_msg"
+	then
+		meld_path="$(git config mergetool.meld.path || echo meld)"
+		meld_help_msg=$($meld_path --help 2>&1)
+	fi
+}
 
-	if meld_has_output_option=$(git config --bool mergetool.meld.hasOutput)
+# Check the features and set flags
+check_meld_for_features () {
+	# Check whether we should use 'meld --output <file>'
+	if test -z "$meld_has_output_option"
 	then
-		: use configured value
-	elif "$meld_path" --help 2>&1 |
-		grep -e '--output=' -e '\[OPTION\.\.\.\]' >/dev/null
+		meld_has_output_option=$(git config --bool mergetool.meld.hasOutput)
+		case "$meld_has_output_option" in
+		true|false)
+			: use configured value
+			;;
+		*)
+			: empty or invalid configured value, detecting "--output" automatically
+			init_meld_help_msg
+
+			case "$meld_help_msg" in
+			*"--output="* | *'[OPTION...]'*)
+				# All version that has [OPTION...] supports --output
+				meld_has_output_option=true
+				;;
+			*)
+				meld_has_output_option=false
+				;;
+			esac
+			;;
+		esac
+	fi
+	# Check whether we should use 'meld --auto-merge ...'
+	if test -z "$meld_use_auto_merge_option"
 	then
-		: old ones mention --output and new ones just say OPTION...
-		meld_has_output_option=true
-	else
-		meld_has_output_option=false
+		meld_use_auto_merge_option=$(git config mergetool.meld.useAutoMerge)
+		case "$meld_use_auto_merge_option" in
+		"")
+			meld_use_auto_merge_option=false
+			;;
+		[Aa]uto)
+			# testing the "--auto-merge" option only if config is "[Aa]uto"
+			init_meld_help_msg
+
+			case "$meld_help_msg" in
+			*"--auto-merge"*)
+				meld_use_auto_merge_option=true
+				;;
+			*)
+				meld_use_auto_merge_option=false
+				;;
+			esac
+			;;
+		*)
+			bool_value=$(git config --bool mergetool.meld.useAutoMerge 2>/dev/null)
+			if test -n "$bool_value"
+			then
+				meld_use_auto_merge_option="$bool_value"
+			else
+				meld_use_auto_merge_option=false
+			fi
+			;;
+		esac
 	fi
 }

base-commit: 07d8ea56f2ecb64b75b92264770c0a664231ce17

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