git-gui: Toggle between new commit and amend commit modes.

I was starting to find it annoying that once you entered the 'Amend Last'
mode there was no way to go back to the 'New Commit' mode without quitting
and restarting git-gui.  Its just confusing for the end-user.

Now we can flip back and forth between a new commit and an amend commit
through a pair of radio buttons on the header of the commit buffer area
and through a pair of radio menu buttons in the Commit menu.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

git-gui

@@ -722,6 +722,16 @@ proc load_last_commit {} {
 	rescan {set ui_status_value {Ready.}}
 }
 
+proc create_new_commit {} {
+	global commit_type ui_comm
+
+	set commit_type normal
+	$ui_comm delete 0.0 end
+	$ui_comm edit modified false
+	$ui_comm edit reset
+	rescan {set ui_status_value {Ready.}}
+}
+
 proc commit_tree {} {
 	global HEAD commit_type file_states ui_comm repo_config
 
@@ -880,7 +890,7 @@ proc commit_writetree {curHEAD msg} {
 
 proc commit_committree {fd_wt curHEAD msg} {
 	global single_commit gitdir HEAD PARENT commit_type tcl_platform
-	global ui_status_value ui_comm
+	global ui_status_value ui_comm selected_commit_type
 	global file_states selected_paths
 
 	gets $fd_wt tree_id
@@ -980,6 +990,7 @@ proc commit_committree {fd_wt curHEAD msg} {
 	# -- Update status without invoking any git commands.
 	#
 	set commit_type normal
+	set selected_commit_type new
 	set HEAD $cmt_id
 	set PARENT $cmt_id
 
@@ -1065,13 +1076,14 @@ Commit or throw away all changes before starting a pull operation.
 }
 
 proc post_pull_remote {remote branch success} {
-	global HEAD PARENT commit_type
+	global HEAD PARENT commit_type selected_commit_type
 	global ui_status_value
 
 	unlock_index
 	if {$success} {
 		repository_state HEAD commit_type
 		set PARENT $HEAD
+		set selected_commit_type new
 		set $ui_status_value "Pulling $branch from $remote complete."
 	} else {
 		set m "Conflicts detected while pulling $branch from $remote."
@@ -1930,8 +1942,22 @@ proc do_signoff {} {
 	}
 }
 
-proc do_amend_last {} {
-	load_last_commit
+proc do_select_commit_type {} {
+	global commit_type selected_commit_type
+
+	if {$selected_commit_type eq {new}
+		&& [string match amend* $commit_type]} {
+		create_new_commit
+	} elseif {$selected_commit_type eq {amend}
+		&& ![string match amend* $commit_type]} {
+		load_last_commit
+
+		# The amend request was rejected...
+		#
+		if {![string match amend* $commit_type]} {
+			set commit_type new
+		}
+	}
 }
 
 proc do_commit {} {
@@ -2450,32 +2476,52 @@ menu .mbar.edit
 # -- Commit Menu
 #
 menu .mbar.commit
+
+.mbar.commit add radiobutton \
+	-label {New Commit} \
+	-command do_select_commit_type \
+	-variable selected_commit_type \
+	-value new \
+	-font font_ui
+lappend disable_on_lock \
+	[list .mbar.commit entryconf [.mbar.commit index last] -state]
+
+.mbar.commit add radiobutton \
+	-label {Amend Last Commit} \
+	-command do_select_commit_type \
+	-variable selected_commit_type \
+	-value amend \
+	-font font_ui
+lappend disable_on_lock \
+	[list .mbar.commit entryconf [.mbar.commit index last] -state]
+
+.mbar.commit add separator
+
 .mbar.commit add command -label Rescan \
 	-command do_rescan \
 	-accelerator F5 \
 	-font font_ui
 lappend disable_on_lock \
 	[list .mbar.commit entryconf [.mbar.commit index last] -state]
-.mbar.commit add command -label {Amend Last Commit} \
-	-command do_amend_last \
-	-font font_ui
-lappend disable_on_lock \
-	[list .mbar.commit entryconf [.mbar.commit index last] -state]
+
 .mbar.commit add command -label {Include Selected Files} \
 	-command do_include_selection \
 	-font font_ui
 lappend disable_on_lock \
 	[list .mbar.commit entryconf [.mbar.commit index last] -state]
+
 .mbar.commit add command -label {Include All Files} \
 	-command do_include_all \
 	-accelerator $M1T-I \
 	-font font_ui
 lappend disable_on_lock \
 	[list .mbar.commit entryconf [.mbar.commit index last] -state]
+
 .mbar.commit add command -label {Sign Off} \
 	-command do_signoff \
 	-accelerator $M1T-S \
 	-font font_ui
+
 .mbar.commit add command -label Commit \
 	-command do_commit \
 	-accelerator $M1T-Return \
@@ -2568,13 +2614,6 @@ pack .vpane.lower.commarea.buttons.rescan -side top -fill x
 lappend disable_on_lock \
 	{.vpane.lower.commarea.buttons.rescan conf -state}
 
-button .vpane.lower.commarea.buttons.amend -text {Amend Last} \
-	-command do_amend_last \
-	-font font_ui
-pack .vpane.lower.commarea.buttons.amend -side top -fill x
-lappend disable_on_lock \
-	{.vpane.lower.commarea.buttons.amend conf -state}
-
 button .vpane.lower.commarea.buttons.incall -text {Include All} \
 	-command do_include_all \
 	-font font_ui
@@ -2597,8 +2636,25 @@ lappend disable_on_lock \
 # -- Commit Message Buffer
 #
 frame .vpane.lower.commarea.buffer
+frame .vpane.lower.commarea.buffer.header
 set ui_comm .vpane.lower.commarea.buffer.t
-set ui_coml .vpane.lower.commarea.buffer.l
+set ui_coml .vpane.lower.commarea.buffer.header.l
+radiobutton .vpane.lower.commarea.buffer.header.new \
+	-text {New Commit} \
+	-command do_select_commit_type \
+	-variable selected_commit_type \
+	-value new \
+	-font font_ui
+lappend disable_on_lock \
+	[list .vpane.lower.commarea.buffer.header.new conf -state]
+radiobutton .vpane.lower.commarea.buffer.header.amend \
+	-text {Amend Last Commit} \
+	-command do_select_commit_type \
+	-variable selected_commit_type \
+	-value amend \
+	-font font_ui
+lappend disable_on_lock \
+	[list .vpane.lower.commarea.buffer.header.amend conf -state]
 label $ui_coml \
 	-anchor w \
 	-justify left \
@@ -2615,6 +2671,10 @@ proc trace_commit_type {varname args} {
 	$ui_coml conf -text $txt
 }
 trace add variable commit_type write trace_commit_type
+pack $ui_coml -side left -fill x
+pack .vpane.lower.commarea.buffer.header.amend -side right
+pack .vpane.lower.commarea.buffer.header.new -side right
+
 text $ui_comm -background white -borderwidth 1 \
 	-undo true \
 	-maxundo 20 \
@@ -2625,7 +2685,7 @@ text $ui_comm -background white -borderwidth 1 \
 	-yscrollcommand {.vpane.lower.commarea.buffer.sby set}
 scrollbar .vpane.lower.commarea.buffer.sby \
 	-command [list $ui_comm yview]
-pack $ui_coml -side top -fill x
+pack .vpane.lower.commarea.buffer.header -side top -fill x
 pack .vpane.lower.commarea.buffer.sby -side right -fill y
 pack $ui_comm -side left -fill y
 pack .vpane.lower.commarea.buffer -side left -fill y
@@ -2897,6 +2957,7 @@ set PARENT {}
 set commit_type {}
 set empty_tree {}
 set current_diff {}
+set selected_commit_type new
 
 wm title . "$appname ([file normalize [file dirname $gitdir]])"
 focus -force $ui_comm