gitk: Add keybinding to switch to parent commit

Signed-off-by: Max Kirillov <max@max630.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
gitk: Updated Bulgarian translation (302t,0f,0u)

Signed-off-by: Alexander Shopov <ash@kambanaria.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Git 2.1-rc2

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'master' of git://ozlabs.org/~paulus/gitk

* 'master' of git://ozlabs.org/~paulus/gitk:
  gitk: Updated Bulgarian translation (302t,0f,0u)
  gitk: Add keybinding to switch to parent commit
avoid SIGPIPE warnings for aliases

When git executes an alias that specifies an external
command, it will complain if the alias dies due to a signal.
This is usually a good thing, as signal deaths are
unexpected. However, SIGPIPE is not unexpected for many
commands which produce a lot of output; it is intended that
the user closing the pager would kill them them via SIGPIPE.

As a result, the user might see annoying messages in a
scenario like this:

  $ cat ~/.gitconfig
  [alias]
  lgbase = log --some-options
  lg = !git lgbase --more-options
  lg2 = !git lgbase --other-options

  $ git lg -p
  [user hits 'q' to exit pager]
  error: git lgbase --more-options died of signal 13
  fatal: While expanding alias 'lg': 'git lgbase --more-options': Success

Many users won't see this, because we execute the external
command with the shell, and a POSIX shell will silently
rewrite the signal-death exit code into 128+signal, and we
will treat it like a normal exit code. However, this does
not always happen:

  1. If the sub-command does not have shell metacharacters,
     we will skip the shell and exec it directly, getting
     the signal code.

  2. Some shells do not do this rewriting; for example,
     setting SHELL_PATH set to zsh will reveal this problem.

This patch squelches the message, and let's git exit
silently (with the same exit code that a shell would use in
case of a signal).

The first line of the message comes from run-command's
wait_or_whine. To silence that message, we remain quiet
anytime we see SIGPIPE.

The second line comes from handle_alias itself. It calls
die_errno whenever run_command returns a negative value.
However, only -1 indicates a syscall error where errno has
something useful (note that it says the useless "success"
above). Instead, we treat negative returns from run_command
(except for -1) as a normal code to be passed to exit.