Add -y/--no-prompt option to mergetool

This option lets git mergetool invoke the conflict resolution program
without waiting for a user prompt each time.

Also added a mergetool.prompt (default true) configuration variable
controlling the same behaviour

Signed-off-by: Charles Bailey <charles@hashpling.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -976,6 +976,9 @@ mergetool.keepBackup::
 	is set to `false` then this file is not preserved.  Defaults to
 	`true` (i.e. keep the backup files).
 
+mergetool.prompt::
+	Prompt before each invocation of the merge resolution program.
+
 pack.window::
 	The size of the window used by linkgit:git-pack-objects[1] when no
 	window size is given on the command line. Defaults to 10.

Documentation/git-mergetool.txt

@@ -7,7 +7,7 @@ git-mergetool - Run merge conflict resolution tools to resolve merge conflicts
 
 SYNOPSIS
 --------
-'git mergetool' [--tool=<tool>] [<file>]...
+'git mergetool' [--tool=<tool>] [-y|--no-prompt|--prompt] [<file>]...
 
 DESCRIPTION
 -----------
@@ -60,6 +60,15 @@ variable `mergetool.<tool>.trustExitCode` can be set to `true`.
 Otherwise, 'git-mergetool' will prompt the user to indicate the
 success of the resolution after the custom tool has exited.
 
+-y or --no-prompt::
+	Don't prompt before each invocation of the merge resolution
+	program.
+
+--prompt::
+	Prompt before each invocation of the merge resolution program.
+	This is the default behaviour; the option is provided to
+	override any configuration settings.
+
 Author
 ------
 Written by Theodore Y Ts'o <tytso@mit.edu>

git-mergetool.sh

@@ -8,7 +8,7 @@
 # at the discretion of Junio C Hamano.
 #
 
-USAGE='[--tool=tool] [file to merge] ...'
+USAGE='[--tool=tool] [-y|--no-prompt|--prompt] [file to merge] ...'
 SUBDIRECTORY_OK=Yes
 OPTIONS_SPEC=
 . git-sh-setup
@@ -176,8 +176,10 @@ merge_file () {
     echo "Normal merge conflict for '$MERGED':"
     describe_file "$local_mode" "local" "$LOCAL"
     describe_file "$remote_mode" "remote" "$REMOTE"
-    printf "Hit return to start merge resolution tool (%s): " "$merge_tool"
-    read ans
+    if "$prompt" = true; then
+	printf "Hit return to start merge resolution tool (%s): " "$merge_tool"
+	read ans
+    fi
 
     case "$merge_tool" in
 	kdiff3)
@@ -280,6 +282,8 @@ merge_file () {
     cleanup_temp_files
 }
 
+prompt=$(git config --bool mergetool.prompt || echo true)
+
 while test $# != 0
 do
     case "$1" in
@@ -295,6 +299,12 @@ do
 		    shift ;;
 	    esac
 	    ;;
+	-y|--no-prompt)
+	    prompt=false
+	    ;;
+	--prompt)
+	    prompt=true
+	    ;;
 	--)
 	    break
 	    ;;