Support for remotes other than origin

[Konboi]

#9

Now av supports only remote origin but I sometimes set multiple remotes and set a name something other than origin

To support it, I added remote and updated to use it

[aviator-app]

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[aviator-app]

FlexReview Summary

Based on the code complexity and the author's expertise score, these are the suggested reviewers:

• @draftcode (current review load: 1)

See the list of alternate reviewers in the detailed breakdown below.

Detailed Breakdown

Author’s expertise score for the modified files:

• cmd/av/commit_common.go (0.00)
• cmd/av/stack_adopt.go (0.00)
• cmd/av/stack_reparent.go (0.00)
• cmd/av/stack_restack.go (0.00)
• cmd/av/stack_sync.go (0.00)
• internal/actions/pr.go (0.00)
• internal/config/config.go (0.00)
• internal/gh/ghui/fetch.go (0.00)
• internal/gh/ghui/push.go (0.00)
• internal/git/git.go (0.00)
• internal/git/git_test.go (0.00)
• internal/git/gitui/prune.go (0.00)

Files	Reviewers
cmd/av/commit_common.go †, cmd/av/stack_adopt.go †, cmd/av/stack_reparent.go †, cmd/av/stack_restack.go †, cmd/av/stack_sync.go †, internal/config/config.go †, internal/gh/ghui/fetch.go †, internal/gh/ghui/push.go †, internal/git/git.go †, internal/git/git_test.go †, internal/git/gitui/prune.go †	@draftcode (score: 1.00, current review load: 1), @jainankit (score: 0.74, current review load: 1)

† Indicates that the file doesn't need an expert review. (?)

See full breakdown of the reviewers on the Aviator webapp.

[Konboi]

Which is better, setting it as the initial value (at here) or checking it here?

[draftcode]

This is fine.