Allow option to change path for cloning in CI

Description

Hello, So I was setting up a pipeline for my go application last weekend, and ran some issues with the GOPATH to build the application and such

Problem

The issue I was having was that the repository was not getting cloned to the correct directory so packages just failed. Now I noticed that it is getting cloned into a specific path Cloning into '/builds/team-name/repo'... and then when I try to run go build I start getting the following errors

main.go:3:8: cannot find package "gitlab.com/team-name/agent/agent" in any of:
	/usr/local/go/src/gitlab.com/team-name/agent/agent (from $GOROOT)
	/go/src/gitlab.com/team-name/agent/agent (from $GOPATH)

Now I get the error of course because the directory structure is not set correctly. For me to fix this issue is that I had to add some scripts in the before_scripts inside of my .gitlab-ci.yml like the following

before_script:
    - mkdir -p /go/src/gitlab.com/team-name/
    - mv ../agent /go/src/gitlab.com/team-name/
    - cd /go/src/gitlab.com/team-name/agent

Now doing the above works fine, until it comes to the end of the job, the runner by default cd back to the /builds/team-name/repo which understandably gives me the following error. Now I understand the reason it is doing this is to upload the artifacts it generates (speculation)

/bin/bash: line 44: cd: /builds/team-name/repo: No such file or directory
ERROR: Build failed: exit code 1

So in every step, I want to run I have to remember to add the step below

 - mv ../agent /builds/team-name/repo

Benefits Cleaner .gitlab-ci.yml file

(Include problem, use cases, benefits, and/or goals)

Proposal

Allow the user to change the default location to where the repository getting cloned so for example in my case it clones the repository to /go/src/gitlab.com/team-name/.

We can use another variable name just like the variable name you use to change the git strategy for example GIT_LOCATION or something that reflects what it is doing better

Links / references

My .gitlab-ci.yml file

image: docker:latest
services:
  - docker:dind

before_script:
    - mkdir -p /go/src/gitlab.com/team-name/
    - mv ../agent /go/src/gitlab.com/team-name/
    - cd /go/src/gitlab.com/team-name/agent

stages:
    - build
    - test

build:
    image: digitalrealms/golang-glide:latest
    stage: build
    script:
        - glide install
        - go build -v -o app
        - mv ../agent /builds/team-name/repo
    artifacts:
        untracked: true

test:
    image: digitalrealms/golang-glide:latest
    stage: test
    script:
        - go test $(glide nv)
        - mv ../agent /builds/digital-realms/agent
    dependencies:
        - build

/cc @grzesiek @tmaczukin

added gitlab-ce19173 gitlab-ce14213 labels

I have similar issue with building libs. I building libs with fixed path and adding them to artifacts. Now i doing this:

1. need copy all cloned data into fixed path. /usr/local/dir
2. do builds and other things.
3. copy created files back into cloned directory for getting artifacts from files.

With setting clone path step 1 and 3 can be removed.

Interesting proposal. Let's move it to the GitLab Runner project, because this is the place we should discuss it.

moved from gitlab-ce#28903