git-gui: Support conflict states _U & UT.

Support _U (local deleted, remote modified) and
UT (file type changed in conflict) modes.

Note that 'file type changed' does not refer to
changes in the executable bit, instead it denotes
replacing a file with a link, or vice versa.

Signed-off-by: Alexander Gavrilov <angavrilov@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

git-gui.sh

@@ -1669,10 +1669,12 @@ foreach i {
 		{D_ {mc "Staged for removal"}}
 		{DO {mc "Staged for removal, still present"}}
 
+		{_U {mc "Requires merge resolution"}}
 		{U_ {mc "Requires merge resolution"}}
 		{UU {mc "Requires merge resolution"}}
 		{UM {mc "Requires merge resolution"}}
 		{UD {mc "Requires merge resolution"}}
+		{UT {mc "Requires merge resolution"}}
 	} {
 	set text [eval [lindex $i 1]]
 	if {$max_status_desc < [string length $text]} {
@@ -1843,7 +1845,7 @@ proc toggle_or_diff {w x y} {
 	# Do not stage files with conflicts
 	if {[info exists file_states($path)]} {
 		set state [lindex $file_states($path) 0]
-		if {[string index $state 0] eq {U}} {
+		if {[string first {U} $state] >= 0} {
 			set col 1
 		}
 	}
@@ -2814,7 +2816,7 @@ proc popup_diff_menu {ctxm ctxmmg x y X Y} {
 	} else {
 		set state {__}
 	}
-	if {[string index $state 0] eq {U}} {
+	if {[string first {U} $state] >= 0} {
 		tk_popup $ctxmmg $X $Y
 	} else {
 		if {$::ui_index eq $::current_diff_side} {

lib/commit.tcl

@@ -151,6 +151,7 @@ The rescan will be automatically started now.
 		D? -
 		T_ -
 		M? {set files_ready 1}
+		_U -
 		U? {
 			error_popup [mc "Unmerged files cannot be committed.
 

lib/diff.tcl

@@ -166,7 +166,7 @@ proc show_diff {path w {lno {}} {scroll_pos {}}} {
 		lappend cmd diff-index
 		lappend cmd --cached
 	} elseif {$w eq $ui_workdir} {
-		if {[string index $m 0] eq {U}} {
+		if {[string first {U} $m] >= 0} {
 			lappend cmd diff
 		} else {
 			lappend cmd diff-files

lib/index.tcl

@@ -164,6 +164,7 @@ proc write_update_index {fd pathList totalCnt batch after} {
 		_O -
 		AM {set new A_}
 		_T {set new T_}
+		_U -
 		U? {
 			if {[file exists $path]} {
 				set new M_