Bugfix checkouting existing branch. Fixes issue #109

[navrkald]

Description

Fixes #109.

Original code did equivalent of following:

git clone <some repo>
git checkout -b <branch name>
git merge --ff origin/<branch name>

new code is properly checkouting remote branch if exists

git clone <some repo>
git fetch
# Try to checkout remote branch
git checkout <branch name>
# If above command fails then new branch is created
git checkout -b <branch name>

Problem with original code is not only that's not convenient, but it's as well bugy, it's silently supposing that <branch name> was created on top of default remote branch name plus it's supposing remote branch name haven't changed in meanwhile until remote <branch name> was created. Ofc this conditions are often not met and thats the case when the bug #109 appears.

TODOs

Read the Gruntwork contribution guidelines.

• Update the docs.
• Run the relevant tests successfully, including pre-commit checks.
• Ensure any 3rd party code adheres with our license policy or delete this line if its not applicable.
• Include release notes. If this PR is backward incompatible, include a migration guide.

Release Notes

Fixed #109 checkout remote branch locally if exists.

[navrkald]

Hi @brikis98 , @hongil0316 It's been 2 months since creation of this PR. Can you please review?

[navrkald]

@ceschae, @james00012, @ZachGoldberg Can you please have a look on this PR?

[denis256]

Create a new branch from the default HEAD, so any existing remote branch history is skipped

[navrkald]

Fist of all thanks @denis256 for review, then please let me describe how new code works.

Code first fetches remote branches, then it tries to checkout existing branch if exist and return from this function on line 204. If checkout of existing branch is not successful then it creates new branch from current HEAD here.

[denis256]

I think PR needs to be updated with changes from master, now it fails on CICD

golang.org/x/tools/cmd/goimports imports
        golang.org/x/tools/internal/imports imports
        golang.org/x/tools/internal/modindex imports
        iter: package iter is not in GOROOT (/usr/local/go/src/iter)
go: downloading golang.org/x/text v0.31.0
go: downloading golang.org/x/net v0.47.0
go: downloading golang.org/x/term v0.37.0
go: downloading github.com/google/go-cmp v0.6.0
go: downloading golang.org/x/crypto v0.44.0

Exited with code exit status 1

I also noticed that there are no tests - I think we need to add such tests, without tests we can't track that checkout of existing branches will continue to work over time

[denis256]

I think there is a risk of losing changes from branches:

• user-1 pushes a branch named new-feature with their recent work.
• user-2 git-xargs on that same new-feature branch.
• Instead of using user-1's branch, the tool ignores it and creates a new, empty branch that also happens to be named new-feature.
• When git-xargs finishes and tries to push, Git will throw an error because user-2 new, empty branch conflicts with your user-1 existing one.

repository/repo-operations.go 207-231

[navrkald]

Again thanks for the review, I will try this week to update tests and back-merge latest master to my branch. How code works I have described in conversation: #149 (comment).