Don't fetch/push upstack branches on av commit create/amend

[oleg-codaio]

Currently, av commit create and av commit amend will sync dependent branches. This also ends up fetching and pushing to the remote in the process, which isn't expected as the remote gets out of sync as the head branch remains unpushed. Syncing with the remote repo ought to happen separately with av stack sync.

Also added some end to end tests for these commands.

Closes #263.

[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: 3)

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

Detailed Breakdown

Author’s expertise score for the modified files:

• cmd/av/commit_amend.go (0.00)
• cmd/av/commit_create.go (0.00)
• e2e_tests/commit_amend_test.go (0.00)
• e2e_tests/commit_create_test.go (0.00)
• e2e_tests/helpers.go (0.00)
• internal/actions/sync_stack.go (0.00)
• internal/git/gittest/commit.go (0.00)
• internal/git/gittest/files.go (0.00)

Files	Reviewers
cmd/av/commit_amend.go †, cmd/av/commit_create.go †, e2e_tests/helpers.go †	@draftcode (score: 1.00, current review load: 3)

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

See full breakdown of the reviewers on the Aviator webapp.