Always convert line endings in `postBuild` to unix

[betatim]

We should filter/convert the line endings in postBuild as that seems to cause problems (see #237 (comment))

Is there a docker option to have it convert line endings on COPY or do we have to convert it before copying or add a tool like dos2unix to the container?

[yuvipanda]

I dunno if we should do this, since then you end up with a postBuild file that works on binder but not locally when run as a script (if I understand correctly). Perhaps a better error message?

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On Thu, Mar 15, 2018 at 11:35 AM, Tim Head ***@***.***> wrote: We should filter/convert the line endings in postBuild as that seems to cause problems (see #237 (comment) <#237 (comment)> ) Is there a docker option to have it convert line endings on COPY or do we have to convert it before copying or add a tool like dos2unix to the container? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#263>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAB23odrwiUv2PwYCwNkj9A5SA0N9NMuks5terRkgaJpZM4SsrPt> .

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[betatim]

I think the problem is that when you checkout a repository on windows you get \r\n as line endings in your files. When you COPY the file into the container (which assumes \n because it is Ubuntu) we are now looking for an executable called /bin/bash\r. Which is where the error comes from.

git generally does the right thing when you checkout files and converts the line endings. In our case that is the source of the problem though.

Explicitly converting to \n inside the container should be "the right thing" to do.

[choldgraf]

yeah the problem is that it will work locally, but not on binder, because the environment binder uses (ubuntu) is different from the one on your computer (windows). I'm of two minds on this, since from the user's perspective, it's feels like it "should" work, but from a developer perspective it's important for users to know the ramifications of file endings.

@betatim what are your intuitions on this? I think I'm generally a +1 so long as we keep a list of "changes we will make to your repo" that we can tell users

[betatim]

I think currently repo2docker will not work on windows because the files get checked out with \r\n, then copied into a docker container (which is linux) and assumes \n. So I think we should always convert inside the container. On binderhub, OSX and linux it would be a no-op as files already have the correct line endings.

[choldgraf]

I think this could be fixed by adding the lines described in this blogpost to the postBuild step. Alternatively do this on the python side by modifying the file with open('postBuild', 'w', newline='\n')

@betatim do you wanna give this a shot?