GNU less can display ANSI-colored text with the -R flag, but this
support has some limitations. One of them is that if an escape
sequence starts on one line and ends on a different line, only the
first line will be colored in less.
As a result, when diff creates colored output with multi-line deletes
or adds, less will only color the first line.
This change resets ANSI color to the default at the end of
each line and restarts it at the beginning of the next. It patches
normal and context mode. Side-by-side already worked in my testing.
* src/context.c (print_context_label, pr_context_hunk): As above.
(pr_unidiff_hunk, print_context_header): Likewise.
* src/normal.c (print_normal_hunk): Likewise.
* tests/colors: Adjust existing tests to accommodate this.
* NEWS (Improvements): Mention it.
Proposed in http://bugs.gnu.org/31105
* tests/colors: Move the TERM=dumb setting into the code run by
"returns_", since some shells do not propagate envvar setting through
to a use of a function like this. That would cause this test to fail
because results were colorized when they should not have been.
Reported by Nelson Beebe.
* src/diff.c (main): With --color or --color=auto, when TERM is
"dumb", disable colorization. Suggested by Daniel Colascione.
* NEWS (Bug fixes): Mention it.
* tests/colors: Add a test that would fail without this change,
yet passes with it.
* tests/colors (epoch): Don't use GNU touch's --date=$epoch option.
Use the portable -t 197001010000.00.
Reported by Assaf Gordon in https://debbugs.gnu.org/24121#8
* tests/colors (e): Fix a portability bug: use printf '\033'
rather than '\e' to generate the required byte sequence, since
for some shells (at least dash 0.5.8), the latter doesn't work.
Work around a shell bug whereby "local tab=$(printf '\t')"
would result in an empty value for "$tab": hoist each "tab"
definition up/out of its function to global scope.
Reported by Assaf Gordon in http://debbugs.gnu.org/24116#8
* src/diff.h (presume_output_tty): New extern variable.
* src/diff.c (PRESUME_OUTPUT_TTY_OPTION): New enum.
(group_format_option): Add '-presume-output-tty'.
(main): Handle PRESUME_OUTPUT_TTY_OPTION.
* src/util.c: New variable `presume_output_tty'.
(check_color_output): Handle presume_output_tty.
(set_color_context): Call process_signals only when color_context is
not RESET_CONTEXT.
* tests/colors: Check that diff doesn't crash when interrupted
in the middle of a color sequence.
Reported by Gisle Vanem in http://debbugs.gnu.org/22067
