fix error handling and return code

[qknight]

Motivation for this change

there is a bug in nix-prefetch-git which makes our implementation of dep2nix impossible, since the error handling is not working at all.

the cause for the problem is that https://golang.org/x/net is not a git repository at all and therefore nix-prefetch-git should fail with an exit code != 0 which is not the case.

the output before the change A

nix-prefetch-git https://golang.org/x/net --rev f5dfe339be1d06f81b22525fe34671ee7d2c8904
Leeres Git-Repository in /tmp/git-checkout-tmp-77RGm6hA/net-f5dfe33/.git/ initialisiert
fatal: https://golang.org/x/net/info/refs not valid: is this a git repository?
fatal: https://golang.org/x/net/info/refs not valid: is this a git repository?
Unable to checkout f5dfe339be1d06f81b22525fe34671ee7d2c8904 from https://golang.org/x/net.
joachim@lenovo-t530 /tmp> echo $status
1

the output before the change A (with --quiet)

nix-prefetch-git https://golang.org/x/net --rev f5dfe339be1d06f81b22525fe34671ee7d2c8904 --quiet
{
  "url": "https://golang.org/x/net",
  "rev": "f5dfe339be1d06f81b22525fe34671ee7d2c8904",
  "date": "",
  "sha256": "0sjjj9z1dhilhpc8pq4154czrb79z9cm044jvn75kxcjv6v5l2m5",
  "fetchSubmodules": true
}
joachim@lenovo-t530 /tmp> echo $status
0

WARNING: exit code should still be 1 and not 0!

the output after the change B

[nix-shell:~/Desktop/projects/nixcloud/dep2nix/src/github.com/nixcloud/dep2nix]$ ./nix-prefetch-git https://golang.org/x/net --rev f5dfe339be1d06f81b22525fe34671ee7d2c8904 
Leeres Git-Repository in /run/user/1000/git-checkout-tmp-9SXKa8i0/net-f5dfe33/.git/ initialisiert
fatal: https://golang.org/x/net/info/refs not valid: is this a git repository?
fatal: https://golang.org/x/net/info/refs not valid: is this a git repository?

[nix-shell:~/Desktop/projects/nixcloud/dep2nix/src/github.com/nixcloud/dep2nix]$ echo $?
1

the output after the change B (with --quiet)

[nix-shell:~/Desktop/projects/nixcloud/dep2nix/src/github.com/nixcloud/dep2nix]$ ./nix-prefetch-git https://golang.org/x/net --rev f5dfe339be1d06f81b22525fe34671ee7d2c8904 --quiet

[nix-shell:~/Desktop/projects/nixcloud/dep2nix/src/github.com/nixcloud/dep2nix]$ echo $?
1

Things done

[aszlig]

@qknight: I'm unable to reproduce this, nix-prefetch-git on https://golang.org/x/net results in the following output with exit code 1:

$ nix-prefetch-git https://golang.org/x/net --rev 9831f2c3ac1068a78f50
Initialized empty Git repository in /tmp/git-checkout-tmp-AREolhSA/net-9831f2c/.git/
fatal: https://golang.org/x/net/info/refs not valid: is this a git repository?
fatal: https://golang.org/x/net/info/refs not valid: is this a git repository?
Unable to checkout 9831f2c3ac1068a78f50 from https://golang.org/x/net.
$ echo $?
1
$ 

You mention https://golang.org/x/net at first but in the example you use https://github.com/ugorji/go. The latter is actually a Git repository.

Do you have the output without these changes applied, but using https://golang.org/x/net?

[qknight]

@aszlig i've fixed the paste above in the OP. sorry that i pasted the wrong output.

[qknight]

i'm not sure if this is the proper solution but it seems to work. can someone confirm this is correct code?

[qknight]

@aszlig i've update the example and you should now be able to see that it is broken and that this PR fixes it.

[mmahut]

What is the status of this pull request?

[mmahut]

Closing due to lack of activity, feel free re-open this if needed.