The width of the commit message text area is currently hard-coded
to 75 characters. This value might be not optimal for some projects.
For instance users who would like to generate GNU-style ChangeLog
file from git commit message might prefer commit messages of width
no longer than 70 characters.

This patch adds a global and per repository option "Commit Message
Text Width", which could be used to change the width of the commit
message text area.
Signed-off-by: NAdam Piątyszek <ediap@users.sourceforge.net>
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>