Highlight common whitespace errors such as whitespace on end of line

Show trailing whitespace (space and/or tab after the end of line,
but before the LF) by displaying it with a red background, so it
stands out visually against the rest of the patch.

Also show tab-after-space within the leading indentation for the
line, as this is an abnormal way to indent a line of code that
usually results in badly formatted code.

Bug: GERRIT-23
Signed-off-by: Shawn O. Pearce <sop@google.com>
4 files changed