Patch was dead simple, so I just created it just in case.
On Thu, Oct 6, 2016 at 2:46 PM, Norbert Kiesel <nkie...@gmail.com> wrote:
> I like the two-step approach. And this is clearly a feature that does not
> need to be rushed. You want me to send a patch for step#1?
>
> On Thu, Oct 6, 2016 at 1:19 PM, Paul Eggert <egg...@cs.ucla.edu> wrote:
>
>> On 10/06/2016 12:48 PM, Norbert Kiesel wrote:
>>
>>> But we should be able to support a GNU_DIFF_FORMAT environment
>>> variable that sets the default format, no?
>>>
>>
>> It might be a good idea to change the default output format. I expect the
>> first step would be to change 'diff' to warn on stderr if no output format
>> option is specified; you could silence the warning with the --normal
>> option, or by setting POSIXLY_CORRECT. This step should also document the
>> first step (and the intent to change the default) in the usual places.
>> After some time in some later release we could then change the default.
>>
>> I'd rather not have diff's behavior depend on a new environment variable.
>> Environment variables are a pain to get right and something like this could
>> break security-relevant code.
>>
>>
>
From 4cd7cbcff3361f0b17db2627301cebc359e02150 Mon Sep 17 00:00:00 2001
From: Norbert Kiesel <nkie...@metricstream.com>
Date: Thu, 6 Oct 2016 15:32:50 -0700
Subject: [PATCH] diff: Warn about future change to default style
diff still uses --normal as default diff style, although this
is no longer recommended to be used and also actually mostly
unused. Thus, futire versions of diff will switch to --unified
as new default style.
This commit only adds a warning informing users of that future
change.
---
NEWS | 7 +++++++
src/diff.c | 7 ++++++-
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/NEWS b/NEWS
index 473332e..ab66ffb 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,13 @@ GNU diffutils NEWS -*-
outline -*-
* Noteworthy changes in release ?.? (????-??-??) [?]
+** New features
+
+ If the diff output style is not set, diff prints a warning that a future
+ release will switch the default output style from --normal to --unified.
This
+ warning can be suppressed by setting the POSIXLY_CORRECT environment variable
+ (though that has some other side effects as well).
+
** Bug fixes
diff no longer mishandles line numbers exceeding 2**31 on Mingw-w64.
diff --git a/src/diff.c b/src/diff.c
index 686945e..12792a1 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -672,7 +672,12 @@ main (int argc, char **argv)
context = 3;
}
else
- specify_style (OUTPUT_NORMAL);
+ {
+ char const *t = getenv ("POSIXLY_CORRECT");
+ if (!t)
+ error (0, 0, _("Future versions of diff will use --unified instead
of --normal as default style"));
+ specify_style (OUTPUT_NORMAL);
+ }
}
if (output_style != OUTPUT_CONTEXT || hard_locale (LC_TIME))
--
2.9.3
