[PATCH v6] Support auto-merge for meld to follow the vim-diff behavior

From: sunlin via GitGitGadget <gitgitgadget@gmail.com>
Date: Jul 2, 2020, 00:44 UTC
Message-ID: <pull.781.v6.git.git.1593650687697.gitgitgadget@gmail.com>
In-Reply-To: <pull.781.v5.git.git.1593587206520.gitgitgadget@gmail.com>

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

Make the mergetool used with "meld" backend behave similarly to how "vimdiff" behavior by telling it to auto-merge parts without conflicts and highlight the parts with conflicts when configuring `mergetool.meld.useAutoMerge` with `true`, or `auto` for automatically detecting the option.

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-v6
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-781/sunlin7/master-v6
Pull-Request: https://github.com/git/git/pull/781

Range-diff vs v5:

 1:  344817d579 ! 1:  63ee3406d2 Enable auto-merge for meld to follow the vim-diff beharior
     @@ Metadata
      Author: Lin Sun <lin.sun@zoom.us>
      
       ## Commit message ##
     -    Enable auto-merge for meld to follow the vim-diff beharior
     +    Support auto-merge for meld to follow the vim-diff behavior
      
     -    Make the mergetool used with "meld" backend behave similarly to
     -    how "vimdiff" behavior by telling it to auto-merge parts without
     -    conflicts and highlight the parts with conflicts when configuring
     -    `mergetool.meld.hasAutoMerge` with `true`, or `auto` for
     -    automatically detecting the option.
     +    Make the mergetool used with "meld" backend behave similarly to how
     +    "vimdiff" behavior by telling it to auto-merge parts without conflicts
     +    and highlight the parts with conflicts when configuring
     +    `mergetool.meld.useAutoMerge` with `true`, or `auto` for automatically
     +    detecting the option.
      
     +    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>
      
       ## Documentation/config/mergetool.txt ##
     @@ Documentation/config/mergetool.txt: mergetool.meld.hasOutput::
       	to `true` tells Git to unconditionally use the `--output` option,
       	and `false` avoids using `--output`.
       
     -+mergetool.meld.hasAutoMerge::
     ++mergetool.meld.useAutoMerge::
      +	Older versions of `meld` do not support the `--auto-merge` option.
     -+	Setting `mergetool.meld.hasOutput` to `true` tells Git to
     -+	unconditionally use the `--auto-merge` option, and `false` avoids using
     -+	`--auto-merge`, and `auto` detect whether `meld` supports `--auto-merge`
     -+	by inspecting the output of `meld --help`, otherwise, follow meld's
     -+	default behavior.
     ++	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
     @@ mergetools/meld: diff_cmd () {
      +	check_meld_for_features
      +
      +	option_auto_merge=
     -+	if test "$meld_has_auto_merge_option" = true
     ++	if test "$meld_use_auto_merge_option" = true
       	then
      -		check_meld_for_output_version
      +		option_auto_merge="--auto-merge"
     @@ mergetools/meld: diff_cmd () {
      -	meld_path="$(git config mergetool.meld.path)"
      -	meld_path="${meld_path:-meld}"
      +# Get meld help message
     -+get_meld_help_msg () {
     -+	meld_path="$(git config mergetool.meld.path || echo meld)"
     -+	$meld_path --help 2>&1
     ++init_meld_help_msg () {
     ++	if test -z "${meld_help_msg:+set}"
     ++	then
     ++		meld_path="$(git config mergetool.meld.path || echo meld)"
     ++		meld_help_msg=$($meld_path --help 2>&1)
     ++	fi
      +}
       
      -	if meld_has_output_option=$(git config --bool mergetool.meld.hasOutput)
     @@ mergetools/meld: diff_cmd () {
      -	elif "$meld_path" --help 2>&1 |
      -		grep -e '--output=' -e '\[OPTION\.\.\.\]' >/dev/null
      +		meld_has_output_option=$(git config --bool mergetool.meld.hasOutput)
     -+		if test "$meld_has_output_option" = true -o \
     -+			"$meld_has_output_option" = false
     -+		then
     ++		case "$meld_has_output_option" in
     ++		true|false)
      +			: use configured value
     -+		else
     -+			# treat meld_has_output_option as "auto"
     -+			if test -z "$meld_help_msg"
     -+			then
     -+				meld_help_msg="$(get_meld_help_msg)"
     -+			fi
     ++			;;
     ++		*)
     ++			: treat meld_has_output_option as "auto"
     ++			init_meld_help_msg
      +
      +			case "$meld_help_msg" in
     -+				*"--output="* | *"[OPTION"???"]"*)
     -+					# old ones mention --output and new ones just say OPTION...
     -+					meld_has_output_option=true ;;
     -+				*)
     -+					meld_has_output_option=false ;;
     ++			*"--output="* | *'[OPTION...]'*)
     ++				# All version that has [OPTION...] supports --output
     ++				meld_has_output_option=true
     ++				;;
     ++			*)
     ++				meld_has_output_option=false
     ++				;;
      +			esac
     -+		fi
     ++			;;
     ++		esac
      +	fi
      +	# Check whether we should use 'meld --auto-merge ...'
     -+	if test -z "${meld_has_auto_merge_option:+set}"
     ++	if test -z "${meld_use_auto_merge_option:+set}"
       	then
      -		: old ones mention --output and new ones just say OPTION...
      -		meld_has_output_option=true
      -	else
      -		meld_has_output_option=false
     -+		meld_has_auto_merge_option=$(git config mergetool.meld.hasAutoMerge)
     -+		if test "$meld_has_auto_merge_option" = auto
     -+		then
     ++		meld_use_auto_merge_option=$(git config mergetool.meld.useAutoMerge)
     ++		case "$meld_use_auto_merge_option" in
     ++		[Tt]rue|[Yy]es|[Oo]n|1)
     ++			meld_use_auto_merge_option=true
     ++			;;
     ++		auto)
      +			# testing the "--auto-merge" option only if config is "auto"
     -+			if test -z "$meld_help_msg"
     -+			then
     -+					meld_help_msg="$(get_meld_help_msg)"
     -+			fi
     ++			init_meld_help_msg
      +
      +			case "$meld_help_msg" in
     -+				*"--auto-merge"*)
     -+					: old ones mention --output and new ones just say OPTION...
     -+					meld_has_auto_merge_option=true ;;
     -+				*)
     -+					meld_has_auto_merge_option=false ;;
     ++			*"--auto-merge"*)
     ++				meld_use_auto_merge_option=true
     ++				;;
     ++			*)
     ++				meld_use_auto_merge_option=false
     ++				;;
      +			esac
     -+		fi
     ++			;;
     ++		*)
     ++			meld_use_auto_merge_option=false
     ++			;;
     ++		esac
       	fi
       }

 Documentation/config/mergetool.txt |  9 ++++
 mergetools/meld                    | 80 ++++++++++++++++++++++++------
 2 files changed, 73 insertions(+), 16 deletions(-)

diff --git a/Documentation/config/mergetool.txt b/Documentation/config/mergetool.txt
index 09ed31dbfa..625ad34230 100644
--- a/Documentation/config/mergetool.txt
+++ b/Documentation/config/mergetool.txt
@@ -30,6 +30,15 @@ mergetool.meld.hasOutput::
 	to `true` tells Git to unconditionally use the `--output` option,
 	and `false` avoids using `--output`.
 
+mergetool.meld.useAutoMerge::
+	Older versions of `meld` do not support the `--auto-merge` option.
+	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..5bc03f564a 100644
--- a/mergetools/meld
+++ b/mergetools/meld
@@ -3,34 +3,82 @@ 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 "${meld_help_msg:+set}"
+	then
+		meld_path="$(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:+set}"
 	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
+			;;
+		*)
+			: treat meld_has_output_option as "auto"
+			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:+set}"
 	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
+		[Tt]rue|[Yy]es|[Oo]n|1)
+			meld_use_auto_merge_option=true
+			;;
+		auto)
+			# testing the "--auto-merge" option only if config is "auto"
+			init_meld_help_msg
+
+			case "$meld_help_msg" in
+			*"--auto-merge"*)
+				meld_use_auto_merge_option=true
+				;;
+			*)
+				meld_use_auto_merge_option=false
+				;;
+			esac
+			;;
+		*)
+			meld_use_auto_merge_option=false
+			;;
+		esac
 	fi
 }

base-commit: 07d8ea56f2ecb64b75b92264770c0a664231ce17

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