[PATCH v3 2/3] mergetools: vimdiff: fix single tab mode, single window mode and colors

[Fernando Ramos <greenfoo@xxxxxx>]

vimdiff3 was introduced in 7c147b77d3 (mergetools: add vimdiff3 mode,
2014-04-20) and then partially broken in 0041797449 (vimdiff: new
implementation with layout support, 2022-03-30) in two ways:

    - It does not show colors unless the user has "set hidden" in his
      .vimrc file

    - It prompts the user to "Press ENTER" every time it runs.

This patch fixes both issues and, in adition:

  - Unifies the previously "special" case where LAYOUT contained one single tab
    with one single window.

  - Fixes colors in tabs with just one window.

Cc: Felipe Contreras <felipe.contreras@xxxxxxxxx>
Signed-off-by: Fernando Ramos <greenfoo@xxxxxx>
---
 mergetools/vimdiff | 69 ++++++++++++++++++++++++++++++++--------------
 1 file changed, 49 insertions(+), 20 deletions(-)

diff --git a/mergetools/vimdiff b/mergetools/vimdiff
index ea416adcaa..f8cd7a83f0 100644
--- a/mergetools/vimdiff
+++ b/mergetools/vimdiff
@@ -55,12 +55,40 @@ substring () {
 	echo "$STRING" | cut -c$(( START + 1 ))-$(( START + $LEN ))
 }
 
+enable_diff_mode () {
+	# Auxiliary function that appends extra vim commands at the end of each
+	# tab section to enable diff mode
+
+	NUMBER_OF_WINDOWS_IN_TAB=$1
+
+	if test "$NUMBER_OF_WINDOWS_IN_TAB" -eq 1
+	then
+		# Tabs that only contains one window will "diff"
+		# against all loaded/hidden buffers
+
+		echo "let tmp=bufnr('%') | execute 'silent 1,4bufdo diffthis' | execute 'buffer '.tmp"
+	else
+		# Tabs that contain more than one window will
+		# only "diff" against those windows
+
+		echo "execute 'windo diffthis'"
+	fi
+}
+
 gen_cmd_aux () {
 	# Auxiliary function used from "gen_cmd()".
 	# Read that other function documentation for more details.
+	#
+	# This function returns two items
+	#    - STDOUT:  The vim command to use
+	#    - RETCODE: The number of windows opened in the current tab
 
-	LAYOUT=$1
-	CMD=$2  # This is a second (hidden) argument used for recursion
+	WINDOWS_NR=$1 # Number of windows opened in the current tab after
+	              # having parsed the provided "LAYOUT"
+	              # If applicable, this variable will be updated and
+	              # returned in RETCODE
+	LAYOUT=$2     # Substring (from the original LAYOUT) to process
+	CMD=$3        # This is a third (hidden) argument used for recursion
 
 	debug_print
 	debug_print "LAYOUT    : $LAYOUT"
@@ -232,6 +260,7 @@ gen_cmd_aux () {
 		after="wincmd j"
 		index=$index_horizontal_split
 		terminate="true"
+		WINDOWS_NR=$(( WINDOWS_NR + 1 ))
 
 	elif ! test -z "$index_vertical_split"
 	then
@@ -239,16 +268,27 @@ gen_cmd_aux () {
 		after="wincmd l"
 		index=$index_vertical_split
 		terminate="true"
+		WINDOWS_NR=$(( WINDOWS_NR + 1 ))
 	fi
 
 	if  test "$terminate" = "true"
 	then
 		CMD="$CMD | $before"
-		CMD=$(gen_cmd_aux "$(substring "$LAYOUT" "$start" "$(( index - start ))")" "$CMD")
+		CMD=$(gen_cmd_aux $WINDOWS_NR "$(substring "$LAYOUT" "$start" "$(( index - start ))")" "$CMD")
+		WINDOWS_NR=$?
+
+		if ! test -z "$index_new_tab"
+		then
+			CMD="$CMD | $(enable_diff_mode $WINDOWS_NR)"
+			WINDOWS_NR=1
+		fi
+
 		CMD="$CMD | $after"
-		CMD=$(gen_cmd_aux "$(substring "$LAYOUT" "$(( index + 1 ))" "$(( ${#LAYOUT} - index ))")" "$CMD")
+		CMD=$(gen_cmd_aux $WINDOWS_NR "$(substring "$LAYOUT" "$(( index + 1 ))" "$(( ${#LAYOUT} - index ))")" "$CMD")
+		WINDOWS_NR=$?
+
 		echo "$CMD"
-		return
+		return $WINDOWS_NR
 	fi
 
 
@@ -280,10 +320,9 @@ gen_cmd_aux () {
 	fi
 
 	echo "$CMD"
-	return
+	return $WINDOWS_NR
 }
 
-
 gen_cmd () {
 	# This function returns (in global variable FINAL_CMD) the string that
 	# you can use when invoking "vim" (as shown next) to obtain a given
@@ -333,25 +372,15 @@ gen_cmd () {
 
 	# Obtain the first part of vim "-c" option to obtain the desired layout
 
-	CMD=$(gen_cmd_aux "$LAYOUT")
-
-
-	# Adjust the just obtained script depending on whether more than one
-	# windows are visible or not
-
-	if echo "$LAYOUT" | grep ",\|/" >/dev/null
-	then
-		CMD="$CMD | tabdo windo diffthis"
-	else
-		CMD="$CMD | bufdo diffthis"
-	fi
+	CMD=$(gen_cmd_aux 1 "$LAYOUT")
+	CMD="$CMD | $(enable_diff_mode $?)"
 
 
 	# Add an extra "-c" option to move to the first tab (notice that we
 	# can't simply append the command to the previous "-c" string as
 	# explained here: https://github.com/vim/vim/issues/9076
 
-	FINAL_CMD="-c \"$CMD\" -c \"tabfirst\""
+	FINAL_CMD="-c \"set hidden diffopt-=hiddenoff diffopt-=closeoff\" -c \"$CMD\" -c \"tabfirst\""
 }
 
 
-- 
2.37.1