Re: [PATCH 2/2] travis-ci: record and skip successfully built trees

> On 28 Dec 2017, at 11:31, SZEDER Gábor <szeder.dev@gmail.com> wrote:
> 
> On Wed, Dec 27, 2017 at 8:35 PM, Lars Schneider
> <larsxschneider@gmail.com> wrote:
>> 
>>> On 27 Dec 2017, at 17:49, SZEDER Gábor <szeder.dev@gmail.com> wrote:
> 
>>> Using an ever-growing flat text file might seem like asking for
>>> trouble on the long run, but it's perfectly adequate for this purpose.
>>> Contributors' topic branches are short-lived in general, so this file
>>> won't grow large enough to cause any issues.  Grepping through several
>>> tens of thousands such lines is sufficiently fast, so not even
>>> git/git's forever living integration branches will cause scalability
>>> issues with the current rate of ~1 push/day for a couple of decades.
>>> And even if we reach the point that this file grows too big, the
>>> caches can be deleted on Travis CI's web interface.
>> 
>> One more thing:
>> Maybe we could delete "$HOME/travis-cache/good-trees" if the file
>> has more than 1000 lines *before* we add a new tree?
>> 
>> Or we use something like this to cap the file:
>> 
>>  echo "$(tail -1000 $HOME/travis-cache/good-trees)" > $HOME/travis-cache/good-trees
> 
> Well, there is always something new to learn.
> I was aware that things like 'cmd file >file' don't work, because the
> shell opens and truncates 'file' before executing the command, so 'cmd'
> will open the already empty file, but I didn't know that 'echo "$(cmd
> file)" >file' works.  Thanks for letting me know.
> 
> However, this is subject to the portability issues of the shell's
> 'echo', i.e. try
> 
>  echo "$(cat git.c)" >git.c
> 
> with Bash and Dash.  Bash produces the exact same contents, but Dash
> turns all '\n' in help and error strings to real newline characters.
> 
> Now, Git's object names will never contain such characters, and most
> likely $TRAVIS_JOB_{NUMBER,ID} won't ever do that, either, so this is
> not an issue for this 'good-trees' file.  Still, I think it'd be better
> to stick to using a good old temporary file:
> 
>  tail -1000 good-trees >tmp
>  mv tmp good-trees