Organizing package.el a bit

[Artur Malabarba <bruce.connor.am@gmail.com>]

Hi All,
Since last time that I worked a bit on package.el, I noticed it's a
little annoying to manage due to sheer size. I understand 2600 lines
is not the largest .el file we have (hell, it's not even top 10), but
it's enough to bother me a lot.

I'd like to know whether it's ok to split it into two files,
package.el and package-menu.el?

The distinction is very logic, there's a ton of stuff that goes on in
package.el which doesn't make any use of the package-menu.
The only downside of this refactoring would be to mess up things like
`git-blame`, and that's why I'm askinghere.

Is that a reason not to do it?

Cheers
Artur