Merge branch 'sh/mergetool-hideresolved'

"git mergetool" feeds three versions (base, local and remote) of
a conflicted path unmodified.  The command learned to optionally
prepare these files with unconflicted parts already resolved.

* sh/mergetool-hideresolved:
  mergetool: add per-tool support and overrides for the hideResolved flag
  mergetool: break setup_tool out into separate initialization function
  mergetool: add hideResolved configuration

Documentation/config/mergetool.txt

@@ -13,6 +13,11 @@ mergetool.<tool>.cmd::
 	merged; 'MERGED' contains the name of the file to which the merge
 	tool should write the results of a successful merge.
 
+mergetool.<tool>.hideResolved::
+	Allows the user to override the global `mergetool.hideResolved` value
+	for a specific tool. See `mergetool.hideResolved` for the full
+	description.
+
 mergetool.<tool>.trustExitCode::
 	For a custom merge command, specify whether the exit code of
 	the merge command can be used to determine whether the merge was
@@ -40,6 +45,16 @@ mergetool.meld.useAutoMerge::
 	value of `false` avoids using `--auto-merge` altogether, and is the
 	default value.
 
+mergetool.hideResolved::
+	During a merge Git will automatically resolve as many conflicts as
+	possible and write the 'MERGED' file containing conflict markers around
+	any conflicts that it cannot resolve; 'LOCAL' and 'REMOTE' normally
+	represent the versions of the file from before Git's conflict
+	resolution. This flag causes 'LOCAL' and 'REMOTE' to be overwriten so
+	that only the unresolved conflicts are presented to the merge tool. Can
+	be configured per-tool via the `mergetool.<tool>.hideResolved`
+	configuration variable. Defaults to `true`.
+
 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

Documentation/git-mergetool--lib.txt

@@ -38,6 +38,10 @@ get_merge_tool_cmd::
 get_merge_tool_path::
 	returns the custom path for a merge tool.
 
+initialize_merge_tool::
+	bring merge tool specific functions into scope so they can be used or
+	overridden.
+
 run_merge_tool::
 	launches a merge tool given the tool name and a true/false
 	flag to indicate whether a merge base is present.

git-difftool--helper.sh

@@ -61,6 +61,9 @@ launch_merge_tool () {
 		export BASE
 		eval $GIT_DIFFTOOL_EXTCMD '"$LOCAL"' '"$REMOTE"'
 	else
+		initialize_merge_tool "$merge_tool"
+		# ignore the error from the above --- run_merge_tool
+		# will diagnose unusable tool by itself
 		run_merge_tool "$merge_tool"
 	fi
 }
@@ -79,6 +82,9 @@ if test -n "$GIT_DIFFTOOL_DIRDIFF"
 then
 	LOCAL="$1"
 	REMOTE="$2"
+	initialize_merge_tool "$merge_tool"
+	# ignore the error from the above --- run_merge_tool
+	# will diagnose unusable tool by itself
 	run_merge_tool "$merge_tool" false
 else
 	# Launch the merge tool on each path provided by 'git diff'

git-mergetool--lib.sh

@@ -166,6 +166,10 @@ setup_tool () {
 		return 1
 	}
 
+	hide_resolved_enabled () {
+		return 0
+	}
+
 	translate_merge_tool_path () {
 		echo "$1"
 	}
@@ -250,6 +254,10 @@ trust_exit_code () {
 	fi
 }
 
+initialize_merge_tool () {
+	# Bring tool-specific functions into scope
+	setup_tool "$1" || return 1
+}
 
 # Entry point for running tools
 run_merge_tool () {
@@ -261,9 +269,6 @@ run_merge_tool () {
 	merge_tool_path=$(get_merge_tool_path "$1") || exit
 	base_present="$2"
 
-	# Bring tool-specific functions into scope
-	setup_tool "$1" || return 1
-
 	if merge_mode
 	then
 		run_merge_cmd "$1"

git-mergetool.sh

@@ -239,6 +239,13 @@ checkout_staged_file () {
 	fi
 }
 
+hide_resolved () {
+	git merge-file --ours -q -p "$LOCAL" "$BASE" "$REMOTE" >"$LCONFL"
+	git merge-file --theirs -q -p "$LOCAL" "$BASE" "$REMOTE" >"$RCONFL"
+	mv -- "$LCONFL" "$LOCAL"
+	mv -- "$RCONFL" "$REMOTE"
+}
+
 merge_file () {
 	MERGED="$1"
 
@@ -265,6 +272,8 @@ merge_file () {
 		ext=
 	esac
 
+	initialize_merge_tool "$merge_tool" || return
+
 	mergetool_tmpdir_init
 
 	if test "$MERGETOOL_TMPDIR" != "."
@@ -276,7 +285,9 @@ merge_file () {
 
 	BACKUP="$MERGETOOL_TMPDIR/${BASE}_BACKUP_$$$ext"
 	LOCAL="$MERGETOOL_TMPDIR/${BASE}_LOCAL_$$$ext"
+	LCONFL="$MERGETOOL_TMPDIR/${BASE}_LOCAL_LCONFL_$$$ext"
 	REMOTE="$MERGETOOL_TMPDIR/${BASE}_REMOTE_$$$ext"
+	RCONFL="$MERGETOOL_TMPDIR/${BASE}_REMOTE_RCONFL_$$$ext"
 	BASE="$MERGETOOL_TMPDIR/${BASE}_BASE_$$$ext"
 
 	base_mode= local_mode= remote_mode=
@@ -322,6 +333,45 @@ merge_file () {
 	checkout_staged_file 2 "$MERGED" "$LOCAL"
 	checkout_staged_file 3 "$MERGED" "$REMOTE"
 
+	# hideResolved preferences hierarchy.
+	global_config="mergetool.hideResolved"
+	tool_config="mergetool.${merge_tool}.hideResolved"
+
+	if enabled=$(git config --type=bool "$tool_config")
+	then
+		# The user has a specific preference for a specific tool and no
+		# other preferences should override that.
+		: ;
+	elif enabled=$(git config --type=bool "$global_config")
+	then
+		# The user has a general preference for all tools.
+		#
+		# 'true' means the user likes the feature so we should use it
+		# where possible but tool authors can still override.
+		#
+		# 'false' means the user doesn't like the feature so we should
+		# not use it anywhere.
+		if test "$enabled" = true && hide_resolved_enabled
+		then
+		    enabled=true
+		else
+		    enabled=false
+		fi
+	else
+		# The user does not have a preference. Ask the tool.
+		if hide_resolved_enabled
+		then
+		    enabled=true
+		else
+		    enabled=false
+		fi
+	fi
+
+	if test "$enabled" = true
+	then
+		hide_resolved
+	fi
+
 	if test -z "$local_mode" || test -z "$remote_mode"
 	then
 		echo "Deleted merge conflict for '$MERGED':"

t/t7610-mergetool.sh

@@ -842,4 +842,22 @@ test_expect_success 'mergetool --tool-help shows recognized tools' '
 	grep meld mergetools
 '
 
+test_expect_success 'mergetool hideResolved' '
+	test_config mergetool.hideResolved true &&
+	test_when_finished "git reset --hard" &&
+	git checkout -b test${test_count}_b main &&
+	test_write_lines >file1 base "" a &&
+	git commit -a -m "base" &&
+	test_write_lines >file1 base "" c &&
+	git commit -a -m "remote update" &&
+	git checkout -b test${test_count}_a HEAD~ &&
+	test_write_lines >file1 local "" b &&
+	git commit -a -m "local update" &&
+	test_must_fail git merge test${test_count}_b &&
+	yes "" | git mergetool file1 &&
+	test_write_lines >expect local "" c &&
+	test_cmp expect file1 &&
+	git commit -m "test resolved with mergetool"
+'
+
 test_done