Support for '--setup-prefix' for path to setup.py

[derks]

For standard python packages, having a setup.py in the root directory of your source repo makes perfect sense. However, I have several large projects that are broken up into multiple installable python packages, within the same git repo. For example:

http://github.com/derks/cement

In the above example, all python installable packages are under a './src/' prefix. The reason for seperate python packages is because of externel dependencies. The core library has zero external dependencies, therefore any extensions that do have external dependencies are packaged seperately, since they are optional extensions... and I don't want to enforce installing external deps for things people don't want.

My issue is, I can not use the '-e' option with this type of git repo because there is no 'setup.py' in the root directory of the git repo. What I would like to see is an added '--setup-prefix' or similar option. For example:

pip install --setup-prefix='./src/cement2' -e git+git://github.com/derks/cement.git#egg=cement2

Or for the other packages for example:

pip install --setup-prefix='./src/cement2.ext.configobj' -e git+git://github.com/derks/cement.git#egg=cement2.ext.configobj

I would imagine that '--setup-prefix' would trigger a simple call to 'os.chdir()' to change the working directory after checkout.

My only alternative is to maintain all secondary python packages (extensions) in their own git repo... which is not ideal because I maintain all as one source (versions, testing, continuous integration, etc). Seems like a relatively simple solution which would allow pip to support 'non-standard' directory structures.

Thank you!

[pnasrat]

See issue #526