Return failure code to the system when commands fail

[nicoddemus]

Currently mu will always return 0 to the system even when the git commands have failed.

While it is definitely good to always try the operations in all repositories (instead of stopping at the first error), always returning 0 to the system makes using 'mu' in scripts difficult, as we cannot easily be sure that the operations were successful.

In addition, this will now print (in red) the repositories where the operation has failed: a very common beginner mistake when using mu is to not notice that the command failed for one of the repositories, as it may end up at the top of the output.

Here is a screenshot of mu checkout foobar where only ben10 has that branch:

[fabioz]

Dae Bruno, tudo certo por ai? Valeu pelo PR :)

[nicoddemus]

Tudo certo Zaza! E contigo cara?

O teste no linux falhou, eu tava vendo agora... quer que eu abra um follow up corrigindo ele?

[fabioz]

Tudo certo :)

Se vc quiser ajuda (nada a ver com este PR).

[fabioz]

Eu mudei o diff para usar o beyond compare por default (bem melhor que o meld...).

[fabioz]

Ops, na verdade tinha 2 falhas... heheh. Valeu, ja fiz o merge.

[jbrwilkinson]

Thanks @nicoddemus this is an excellent addition. For the final sys.exit, do you think it is worth returning the total number of failures, rather than 1 (some number failed) or 0 (everything succeeded)?

[nicoddemus]

For the final sys.exit, do you think it is worth returning the total number of failures, rather than 1 (some number failed) or 0 (everything succeeded)?

I don't have the need for that, but I can see it being useful yes. Feel free to open a follow-up PR changing that. 👍