ui: add new config option for help text width
Before this patch, when printing help text using `hg help`, or `hg log -h`,
the output will wrap at 78 chars even if the user has a bigger terminal width
and there is no config option to change it, making the experience different
from the commonly used `man` tool.
This patch introduces a new config option `ui.textwidth`, which replaces the
hardcoded number. It's set to 78 by default to maintain compatibility. When
set to 0, `hg help` will behave more like `man`.
# invalid filenames
test-add.t
test-init.t
test-clone.t
test-contrib.t
test-hgweb-raw.t
test-walk.t
# no sockets or fifos
test-hup.t
# no hardlinks
test-hardlinks.t
test-relink.t
# exec bit problems
test-convert-bzr-114.t
test-convert-bzr-directories.t
test-convert-bzr-merges.t
test-convert-bzr-treeroot.t
test-convert-darcs.t
test-merge-tools.t
# debugstate exec bit false positives
test-dirstate.t
test-filebranch.t
test-merge-remove.t