Improve progress reporting during checkout

[rsdunlapiv]

Summary of Issue:

Big repos take a long time to check out and it may look like the manage_externals is hanging

Expected behavior and actual behavior:

The improved behavior is to add a % complete that is periodically updated when checking out a large repository. This would provide some feedback to the user.

Steps to reproduce the problem (should include model description file(s) or link to publi c repository):

Check out any External with a large repo, such as a lot of submodules.

[gold2718]

From a purely technical point of view, do you have any idea how to do this?
https://stackoverflow.com/questions/4640020/progress-indicator-for-git-clone#4640045

[billsacks]

git clone does give you a progress report when running it interactively, but I'm not sure if / how it would be possible to harvest and echo that information when running it from within manage_externals. I like this idea, but I'm also curious if @rsdunlapiv has any ideas about how we might do this.

[gold2718]

As mentioned in the StackOverflow article linked above, the progress counter is only for step 2 of a 4 step clone process and even that is approximate as it is a percent of objects transmitted, not the data volume transmitted. Step 1 can take quite a while for a repo with a deep and/or complex commit tree.