[PATCH (GIT-GUI,GITK) 0/8] Encoding support in GUI

Currently GUI tools don't provide any support for viewing files that contain non-ASCII characters. This set of patches addresses that issue. The git-gui part of the series is based on patches that are currently in the 'pu' branch of the git-gui repository.

File encoding can be specified in the following ways:

1) It defaults to the current locale encoding.
2) It can be overridden by setting the gui.encoding option.
3) It can be further set on per-file basis by specifying
   the 'encoding' attribute in gitattributes.
4) Finally, git-gui allows directly selecting encodings
   through a popup menu.

The last item is a necessity to compensate for the fact that now staging/unstaging hunks would not work, if the selected encoding is incompatible with the actual data:

While most single-byte character sets are mutually compatible, all multibyte encodings, including utf-8, have the concept of invalid byte sequences, and thus are not completely reversible. Because of this, git-gui won't be able to apply hunks that contain such sequences, and the user would have to specify the encoding correctly, or fallback to ISO-8859-1.

Since git apparently cannot work with filenames in non-locale encodings anyway, I did not try to do anything about it apart from fixing some obvious bugs.

There are also some bugs in handling of commit encodings in gitk, but they are out of the scope of this series.

GIT-GUI:
	git-gui: Cleanup handling of the default encoding.
	---
	git-gui.sh       |    1 +
	lib/blame.tcl    |    2 +-
	lib/diff.tcl     |   11 ++++++-----
	lib/encoding.tcl |   14 ++++++++++++++
	lib/option.tcl   |   24 ++++++++++++++++++++++++
	5 files changed, 46 insertions(+), 6 deletions(-)

	git-gui: Add a menu of available encodings.
	---
	lib/encoding.tcl |  133 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
	lib/option.tcl   |   13 +++++-
	2 files changed, 142 insertions(+), 4 deletions(-)

	git-gui: Allow forcing display encoding for diffs using a submenu.
	---
	git-gui.sh       |    8 ++++++++
	lib/diff.tcl     |    9 +++++++++
	lib/encoding.tcl |   29 +++++++++++++++++++++++++++--
	3 files changed, 44 insertions(+), 2 deletions(-)

	git-gui: Optimize encoding name resolution using a lookup table.
	---
	lib/encoding.tcl |   82 +++++++++++++++++++++++++++++++++++-------------------
	1 files changed, 53 insertions(+), 29 deletions(-)

	git-gui: Support the encoding menu in gui blame.
	---
	lib/blame.tcl |   17 +++++++++++++++++
	1 files changed, 17 insertions(+), 0 deletions(-)

GITK:
	gitk: Port new encoding logic from git-gui.
	---
	gitk |   50 +++++++++++++++++++++++++++++++++++++++++++++++---
	1 files changed, 47 insertions(+), 3 deletions(-)

	gitk: Implement file contents encoding support.
	---
	gitk |   19 ++++++++++++++++---
	1 files changed, 16 insertions(+), 3 deletions(-)

	gitk: Support filenames in the locale encoding.
	---
	gitk |   16 +++++++++++-----
	1 files changed, 11 insertions(+), 5 deletions(-)