Mark strings for translation.

The procedure [mc ...] will translate the strings through msgcat.
Strings must be enclosed in quotes, not in braces, because otherwise
xgettext cannot extract them properly, although on the Tcl side both
delimiters would work fine.

[jes: I merged the later patches to that end.]

Signed-off-by: Christian Stimming <stimming@tuhh.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
diff --git a/lib/diff.tcl b/lib/diff.tcl
index e09e125..b1129d5 100644
--- a/lib/diff.tcl
+++ b/lib/diff.tcl
@@ -39,13 +39,13 @@
 	set s $file_states($path)
 	if {[lindex $s 0] ne {_M}} return
 
-	info_popup "No differences detected.
+	info_popup [mc "No differences detected.
 
-[short_path $path] has no changes.
+%s has no changes.
 
 The modification date of this file was updated by another application, but the content within the file was not changed.
 
-A rescan will be automatically started to find other files which may have the same state."
+A rescan will be automatically started to find other files which may have the same state." [short_path $path]]
 
 	clear_diff
 	display_file $path __
@@ -94,7 +94,7 @@
 			set diff_active 0
 			unlock_index
 			ui_status "Unable to display [escape_path $path]"
-			error_popup "Error loading file:\n\n$err"
+ 		    error_popup [append [mc "Error loading file:"] "\n\n$err"]
 			return
 		}
 		$ui_diff conf -state normal
@@ -159,7 +159,7 @@
 		set diff_active 0
 		unlock_index
 		ui_status "Unable to display [escape_path $path]"
-		error_popup "Error loading diff:\n\n$err"
+		error_popup [append [mc "Error loading diff:"] "\n\n$err"]
 		return
 	}
 
@@ -275,14 +275,14 @@
 	set apply_cmd {apply --cached --whitespace=nowarn}
 	set mi [lindex $file_states($current_diff_path) 0]
 	if {$current_diff_side eq $ui_index} {
-		set mode unstage
+		set failed_msg [mc "Failed to unstage selected hunk."]
 		lappend apply_cmd --reverse
 		if {[string index $mi 0] ne {M}} {
 			unlock_index
 			return
 		}
 	} else {
-		set mode stage
+		set failed_msg [mc "Failed to stage selected hunk."]
 		if {[string index $mi 1] ne {M}} {
 			unlock_index
 			return
@@ -307,7 +307,7 @@
 		puts -nonewline $p $current_diff_header
 		puts -nonewline $p [$ui_diff get $s_lno $e_lno]
 		close $p} err]} {
-		error_popup "Failed to $mode selected hunk.\n\n$err"
+		error_popup [append $failed_msg "\n\n$err"]
 		unlock_index
 		return
 	}