Support "--nohooks" on fetch

Support "--nohooks" on fetch

Add a way to prevent gclient's hooks from running after `fetch`, to allow
installation of build dependencies between the initial `gclient sync` and the
execution of the hooks.

[agable, 2013-04-17 17:10:40]

One coding comment inline.

I have one question and one main comment.

Question: what is the use-case that you see for this? Our goal with fetch is to
get developers everything they need to work on a given project (fetch will
support way more than just Chromium and Blink in the near future) in a single
command. Splitting that process -- fetch, install build deps, sync -- seems like
unnecessary complication. What caused you to want to split the process like
that?

Comment: I'm unconvinced we want a nohooks flag... especially since fetch will
soon support bare Git and Svn checkouts. Since those don't use gclient, there's
no meaning to 'nohooks', so having it as a global flag to fetch doesn't make
sense. This implementation is reasonable given that fetch currently only has
GclientGit and GclientGitSvn, but it will cause problems in the future as we
expand.

I'd suggest we hold off on adding this flag until after I add proper options
parsing and support for bare Git checkouts. WDYT?

https://codereview.chromium.org/14087013/diff/1/fetch.py
File fetch.py (right):

https://codereview.chromium.org/14087013/diff/1/fetch.py#newcode219
fetch.py:219: argv.pop(1)
I'm going to do a full rewrite of the fetch and recipe options handling using
optparse/argparse. But since that's not in yet, the way options are parsed here
forces them to be in a specific order. The help / dry-run / nohooks options
should be in a loop so they can come in any order.

[Dirk Pranke, 2013-04-17 18:57:20]

I am also curious what is prompting the desire for this flag.

[janx, 2013-04-17 20:15:02]

Thanks for the feedback. The reason I submitted this patch was to give the
opportunity to install build dependencies before running the hooks. For example,
on Ubuntu the previous checkout process was:

    gclient sync --nohooks --jobs=32
    ./src/build/install-build-deps.sh
    gclient runhooks

Which I thought about converting to:

    fetch --nohooks blink
    ./src/build/install-build-deps.sh
    gclient runhooks

Another example of this can be found in the chromium build instructions for
Android:

    gclient sync --nohooks
    . build/android/envsetup.sh
    gclient runhooks

https://code.google.com/p/chromium/wiki/AndroidBuildInstructions actually
indicates that "you should avoid running gclient hooks when syncing for the
first time, as the setup for these tools is not complete until
build/android/envsetup.sh has been run".

But since the role of fetch is to eventually automate everything, this patch
might be unnecessary. Will fetch be checking that build dependencies are
properly installed before running gclient's hooks? Or will the hooks disappear
altogether?

[agable, 2013-04-17 21:36:21]

You may also want to take a look at the comments on
https://codereview.chromium.org/13976012/, which was trying to address this same
issue in a different way.

I think this is the best plan:
* I've got a CL in the works to make fetch always run gclient --nohooks. That's
more in line with the "fetch only does fetching" philosophy. I'll make sure
you're CC'd on that CL, as it will satisfy your use-case.
* Dirk and others (myself included) would like to create a chromium-specific
"just get me everything!" script. That one would run 'fetch chromium;
install_build_deps; gclient runhooks', essentially. That way developers can use
whichever one they prefer, depending on their current setup.

[janx, 2013-04-17 22:10:59]

Thanks for the pointer to the other issue.

I agree with you on both points, and since I already wrote a chromium-specific
"just get me everything!" script I'd like to help out if I can. I suppose this
will be written in Python to be cross-platform?

[agable, 2013-04-17 22:23:36]

Yes, it would definitely be in Python, along with the accompanying linux and
windows (.bat) executable wrappers. I'd be happy to help with a python wrapper
script specifically for chromium that executes fetch, installs build deps, and
runs hooks, but the majority of my time is going to be spent improving fetch and
building other similar tools for other steps of the development process.

[janx, 2013-04-17 22:45:34]

Thanks a lot Aaron! I'll close this issue and wait for --nohooks to become
default.