git-gui: Cleanup handling of the default encoding.

- Make diffs and blame default to the system (locale)
  encoding instead of hard-coding UTF-8.
- Add a gui.encoding option to allow overriding it.
- gitattributes still have the final word.

The rationale for this is Windows support:

1) Windows people are accustomed to using legacy encodings
   for text files. For many of them defaulting to utf-8
   will be counter-intuitive.
2) Windows doesn't support utf-8 locales, and switching
   the system encoding is a real pain. Thus the option.

This patch also adds proper encoding conversion to Apply Hunk/Line.

Signed-off-by: Alexander Gavrilov <angavrilov@gmail.com>
Tested-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

git-gui.sh

@@ -678,6 +678,7 @@ set default_config(merge.verbosity) 2
 set default_config(user.name) {}
 set default_config(user.email) {}
 
+set default_config(gui.encoding) [encoding system]
 set default_config(gui.matchtrackingbranch) false
 set default_config(gui.pruneduringfetch) false
 set default_config(gui.trustmtime) false

lib/blame.tcl

@@ -402,7 +402,7 @@ method _load {jump} {
 	fconfigure $fd \
 		-blocking 0 \
 		-translation lf \
-		-encoding [tcl_encoding [gitattr $path encoding UTF-8]]
+		-encoding [get_path_encoding $path]
 	fileevent $fd readable [cb _read_file $fd $jump]
 	set current_fd $fd
 }

lib/diff.tcl

@@ -164,11 +164,10 @@ proc show_other_diff {path w m scroll_pos} {
 					set sz [string length $content]
 				}
 				file {
-					set enc [gitattr $path encoding UTF-8]
 					set fd [open $path r]
 					fconfigure $fd \
 						-eofchar {} \
-						-encoding [tcl_encoding $enc]
+						-encoding [get_path_encoding $path]
 					set content [read $fd $max_sz]
 					close $fd
 					set sz [file size $path]
@@ -282,7 +281,7 @@ proc start_show_diff {scroll_pos {add_opts {}}} {
 	set ::current_diff_inheader 1
 	fconfigure $fd \
 		-blocking 0 \
-		-encoding [tcl_encoding [gitattr $path encoding UTF-8]] \
+		-encoding [get_path_encoding $path] \
 		-translation lf
 	fileevent $fd readable [list read_diff $fd $scroll_pos]
 }
@@ -435,8 +434,9 @@ proc apply_hunk {x y} {
 	}
 
 	if {[catch {
+		set enc [get_path_encoding $current_diff_path]
 		set p [eval git_write $apply_cmd]
-		fconfigure $p -translation binary -encoding binary
+		fconfigure $p -translation binary -encoding $enc
 		puts -nonewline $p $current_diff_header
 		puts -nonewline $p [$ui_diff get $s_lno $e_lno]
 		close $p} err]} {
@@ -604,8 +604,9 @@ proc apply_line {x y} {
 	set patch "@@ -$hln,$n +$hln,[eval expr $n $sign 1] @@\n$patch"
 
 	if {[catch {
+		set enc [get_path_encoding $current_diff_path]
 		set p [eval git_write $apply_cmd]
-		fconfigure $p -translation binary -encoding binary
+		fconfigure $p -translation binary -encoding $enc
 		puts -nonewline $p $current_diff_header
 		puts -nonewline $p $patch
 		close $p} err]} {

lib/encoding.tcl

@@ -274,3 +274,17 @@ proc tcl_encoding {enc} {
     }
     return {}
 }
+
+proc get_path_encoding {path} {
+	set tcl_enc [tcl_encoding [get_config gui.encoding]]
+	if {$tcl_enc eq {}} {
+		set tcl_enc [encoding system]
+	}
+	if {$path ne {}} {
+		set enc2 [tcl_encoding [gitattr $path encoding $tcl_enc]]
+		if {$enc2 ne {}} {
+			set tcl_enc $enc2
+		}
+	}
+	return $tcl_enc
+}

lib/option.tcl

@@ -1,6 +1,28 @@
 # git-gui options editor
 # Copyright (C) 2006, 2007 Shawn Pearce
 
+proc config_check_encodings {} {
+	global repo_config_new global_config_new
+
+	set enc $global_config_new(gui.encoding)
+	if {$enc eq {}} {
+		set global_config_new(gui.encoding) [encoding system]
+	} elseif {[tcl_encoding $enc] eq {}} {
+		error_popup [mc "Invalid global encoding '%s'" $enc]
+		return 0
+	}
+
+	set enc $repo_config_new(gui.encoding)
+	if {$enc eq {}} {
+		set repo_config_new(gui.encoding) [encoding system]
+	} elseif {[tcl_encoding $enc] eq {}} {
+		error_popup [mc "Invalid repo encoding '%s'" $enc]
+		return 0
+	}
+
+	return 1
+}
+
 proc save_config {} {
 	global default_config font_descs
 	global repo_config global_config
@@ -130,6 +152,7 @@ proc do_options {} {
 		{i-1..99 gui.diffcontext {mc "Number of Diff Context Lines"}}
 		{i-0..99 gui.commitmsgwidth {mc "Commit Message Text Width"}}
 		{t gui.newbranchtemplate {mc "New Branch Name Template"}}
+		{t gui.encoding {mc "Default File Contents Encoding"}}
 		} {
 		set type [lindex $option 0]
 		set name [lindex $option 1]
@@ -275,6 +298,7 @@ proc do_restore_defaults {} {
 }
 
 proc do_save_config {w} {
+	if {![config_check_encodings]} return
 	if {[catch {save_config} err]} {
 		error_popup [strcat [mc "Failed to completely save options:"] "\n\n$err"]
 	}