Hi Geert,
On 8/2/19 1:44 AM, Geert Uytterhoeven wrote:
> Hi Frank,
>
> On Thu, Aug 1, 2019 at 9:55 PM Frank Rowand <frowand.list@xxxxxxxxx> wrote:
>> On 8/1/19 5:13 AM, Geert Uytterhoeven wrote:
>>> On Wed, Jul 31, 2019 at 10:30 PM Frank Rowand <frowand.list@xxxxxxxxx> wrote:
>>>> On 7/31/19 5:37 AM, Geert Uytterhoeven wrote:
>>>>> Add new -c/--color options, to enhance the diff output with color, and
>>>>> improve the user's experience.
>>>>>
>>>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>>>>> ---
>>>>> scripts/dtc/dtx_diff | 10 +++++++++-
>>>>> 1 file changed, 9 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/scripts/dtc/dtx_diff b/scripts/dtc/dtx_diff
>>>>> index e9ad7834a22d9459..4e2c8617f69a333e 100755
>>>>> --- a/scripts/dtc/dtx_diff
>>>>> +++ b/scripts/dtc/dtx_diff
>>>>> @@ -20,6 +20,8 @@ Usage:
>>>>>
>>>>>
>>>>> --annotate synonym for -T
>>>>> + --color synonym for -c
>>>>> + -c enable colored output
>>>>> -f print full dts in diff (--unified=99999)
>>>>> -h synonym for --help
>>>>> -help synonym for --help
>>>
>>>> I like the idea, but...
>>>>
>>>> I have various linux distro releases across my many systems, but only one is
>>>> new enough to have the diff command that supports --color.
>>>
>>> Seems to have been added in diffutils release 3.4 (2016-08-08).
>>> I almost can't believe it was that recent, but then I remembered using a
>>> wrapper before (colordiff; other wrappers may exist).
>>>
>>>> Can you enhance this patch to test whether --color is supported? Maybe
>>>> something like (untested):
>>>>
>>>> -c | --color )
>>>> if `diff --color <(echo a) <(echo a) 2>/dev/null` ; then
>>>> diff_color="--color=always"
>>>> fi
>>>> shift
>>>> ;;
>>>>
>>>> Then add some text to the usage for -c and --color saying that they will
>>>> be silently ignored if diff does not support --color.
>>>>
>>>> I first wrote up a suggested version that printed an error message and
>>>> exited, but I think silently ignoring is more robust, even though it
>>>> may be more confusing to someone who is wondering why --color does not
>>>> work.
>>>
>>> Given this is an optional feature, to be enabled explicitly by the user,
>>> I'm not so fond of going through hoops to auto-detect the availability.
>>>
>>> So what about just documenting this in the help text instead?
>>>
>>> - -c enable colored output
>>> + -c enable colored output (requires diff with --color support)
>>
>> ----- thought 1 -----
>>
>> My first thought was:
>>
>> If the hoops were complex and ugly, I might agree with you. But since it is
>> a simple one line "if" (two lines including "fi") I prefer the check.
>>
>> The help text update looks good to me, along with the check.
>
> OK.
>
>> ----- thought 2 -----
>>
>> Then I reconsidered, and thought "well, Geert has a good idea". So I
>> decided to see how useful the diff error message would be. The message is:
>>
>> $ scripts/dtc/dtx_diff -c a.dts b.dts
>> diff: unrecognized option '--color=always'
>> diff: Try 'diff --help' for more information.
>> $
>> Possible hints to resolve the above error:
>> (hints might not fix the problem)
>>
>> No hints available.
>>
>> It is interesting that the shell prompt arrives before the full set of
>> messages from the script, but that is not my issue. My issue is that
>
> That is due to the output coming from the two "<(compile_to_dts ...)"
> sub-processes, not from the diff sub-process.
Thanks for figuring that out (or knowing it). I figured it probably
was from some sort of separate process issue, but had not chased it
down. Now I have a reminder in the back of my brain to be aware of
messages coming from the "<()" construct.
>
>> when the diff fails, the script tries to find suggestions to solve
>> the problem. (The suggestions exist to catch some likely problems
>> with the shell variable "ARCH".)
>
> Interesting. I didn't know about the hints (never saw them), and had to
> try hard to trigger them (I usually do DTB comparisons only).
> But I succeeded ;-)
> With a small tweak as my diff does support --color:
>
> $ scripts/dtc/dtx_diff -c
> arch/arm64/boot/dts/renesas/r8a7799*{ebisu,draak}.dts
> diff: unrecognized option '--olor=always'
> diff: Try 'diff --help' for more information.
> $
> Possible hints to resolve the above error:
> (hints might not fix the problem)
>
> shell variable $ARCH not set
>
> architecture arm64 is in file path,
> but does not match shell variable $ARCH
> >>$ARCH<< is: >><<
>
>
> Possible hints to resolve the above error:
> (hints might not fix the problem)
>
> shell variable $ARCH not set
>
> architecture arm64 is in file path,
> but does not match shell variable $ARCH
> >>$ARCH<< is: >><<
>
>> Unfortunately in the case of the "--color" problem, the useful warning
>> from diff becomes less visible because of the early prompt and the
>> not so helpful messages about hints.
>
> Yeah, they are not so helpful.
> In fact $ARCH is indeed not set, but that's not an issue at all.
>
>> If the hints related messages were not present, then I was ready to
>> accept that the diff warning was sufficient. But since the hints
>> messages are present, and hiding them would be more complex than
>> the original check that I suggested for whether diff supports
>> the --color option, I am back to my first thought: I prefer the
>> check whether diff supports "--color" is done when dtx_diff detects
>> the "--color" option.
>
> OK, you managed to convince me. Will fix.
Thanks.
>
> Gr{oetje,eeting}s,
>
> Geert
>
