[PATCH (GITK)] gitk: Fix commit encoding support.

[Alexander Gavrilov <angavrilov@gmail.com>]

This commit fixes two problems with commit encodings:

1) git-log actually uses i18n.logoutputencoding to generate
   its output, and falls back to i18n.commitencoding only
   when that option is not set. Thus, gitk should use its
   value to read the results, if available.

2) The readcommit function did not process encodings at all.
   This led to randomly appearing misconverted commits if
   the commit encoding differed from the current locale.

Now commit messages should be displayed correctly, except
when logoutputencoding is set to an encoding that cannot
represent charecters in the message. For example, it is
impossible to convert Japanese characters from Shift-JIS
to CP-1251 (although the reverse conversion works).

Signed-off-by: Alexander Gavrilov <angavrilov@gmail.com>
---
 gitk |   25 +++++++++++++++++++++++--
 1 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/gitk b/gitk
index ae775b1..3834fc0 100755
--- a/gitk
+++ b/gitk
@@ -1555,9 +1555,27 @@ proc chewcommits {} {
     return 0
 }
 
+proc do_readcommit {id} {
+    global tclencoding
+
+    # Invoke git-log to handle automatic encoding conversion
+    set fd [open [concat | git log --no-color --pretty=raw -1 $id] r]
+    # Read the results using i18n.logoutputencoding
+    fconfigure $fd -translation lf -eofchar {}
+    if {$tclencoding != {}} {
+	fconfigure $fd -encoding $tclencoding
+    }
+    set contents [read $fd]
+    close $fd
+    # Remove the heading line
+    regsub {^commit [0-9a-f]+\n} $contents {} contents
+
+    return $contents
+}
+
 proc readcommit {id} {
-    if {[catch {set contents [exec git cat-file commit $id]}]} return
-    parsecommit $id $contents 0
+    if {[catch {set contents [do_readcommit $id]}]} return
+    parsecommit $id $contents 1
 }
 
 proc parsecommit {id contents listed} {
@@ -10565,6 +10583,9 @@ set gitencoding {}
 catch {
     set gitencoding [exec git config --get i18n.commitencoding]
 }
+catch {
+    set gitencoding [exec git config --get i18n.logoutputencoding]
+}
 if {$gitencoding == ""} {
     set gitencoding "utf-8"
 }
-- 
1.6.0.3.15.gb8d36