Fix backend URL parsing

Our fancy custom flag parser broke in Go 1.7. Also, the new 'strict
TCP connection' feature was not handling backend hosts like
`localhost:3000` (it was panicking).

Fixes:

https://gitlab.com/gitlab-org/gitlab-workhorse/issues/54
https://gitlab.com/gitlab-org/gitlab-workhorse/issues/53

See merge request !61

Fix typo in header name



See merge request !59

Strict roundtripper

Workhorse usually connects to Rails over a Unix socket. This makes it
impossible to accidentally follow redirects to another host. This
change applies the same strictness when connecting to Rails over TCP.


See merge request !56

Make "go test" work without path helper



See merge request !57

Workhorse usually connects to Rails over a Unix socket. This makes it
impossible to accidentally follow redirects to another host. This
change applies the same strictness when connecting to Rails over TCP.

Improve support for standard Go tools



See merge request !55

Use Injecter to send entry instead of calling GitLab API

Implement https://gitlab.com/gitlab-org/gitlab-ce/issues/19224

I failed to update `internal/artifacts/artifact_download_test.go` :( Still trying how to fix that and `main_test.go`

See merge request !53

Use URL-safe base64 in mock senddata headers

Rails sends URL-safe encoded base64 so our tests that mock Rails should do the same.

See merge request !54

https://gitlab.com/gitlab-org/gitlab-workhorse/merge_requests/53#note_12984149

TODO: Fix tests!

Mention gmake



See merge request !52

Added GL_PROTOCOL as an ENV variable to gitCommand

With this MR we are now populating an ENV variable called `GL_PROTOCOL` when calling the `gitCommand` method. This will allow GitLab to allow or deny the request based on the allowed Git access protocols defined in the Application Settings.

This MR is needed for:

gitlab-org/gitlab-shell!62 

gitlab-org/gitlab-ce!4696

gitlab-org/gitlab-ce#18601

See merge request !51

Add link to "brief history" blog post in README



See merge request !50

Workhorse to serve the output for format-patch

Now this is done by Rails which is sad for the Unicorn worker, so this
is moved here. This commit excludes tests for now, which will be added
after the weekend.

Part of fixing: gitlab-org/gitlab-ce#13999

See merge request !48