checking out a commits on port quarterly branch

[Marc Branchaud]

Hi Dan,

You're doing it right, assuming that you're not going to be adding any 
new work atop that checked-out commit.  Your working copy does indeed 
reflect the code as of commit 46433baae934d92698422495b72f811839caa1a9.

I've found that the best way to think of git branches is simply as a 
label for a particular commit SHA ID.  Git has other ways of labeling a 
commit (notably tags, and you can actually create your own, separate 
sets of labels if you like).  Git internally calls these labels "refs". 
  The special thing about a branch "ref" is that, when you have the 
branch checked-out and create a new commit, git automatically updates 
the branch's label to refer to the new commit.

But you can also checkout a commit using its SHA ID, as you did.  In 
this case you are not using a branch, so git is warning you that it is 
not tracking a name for any new commits you might create.  Git still 
lets you do anything you want in this "detached" state, with the caveat 
that if you make new commits then it's up to you to figure out how to 
keep track of them (SHA IDs being a bit hard to memorize).  BTW, 
checking out a tag also puts git into the "detached" state, because tags 
are considered static and so they do not get automatically updated when 
you add new commits.

For regular development it's important to understand when you're in the 
"detached" state, because it's easy to lose your work.  Hence the big 
warning message (which you can disable).  But if you're just looking to 
build the code at a particular commit, you're fine being "detached" from 
any actual branch.

		M.


On 2020-11-18 5:30 p.m., Dan Langille wrote:
> When FreshPorts processes a commit, it needs a working copy of the repo as it was at the time of that commit.
> 
> I have this working on head. I am trying to figure out how to do that when the commit is on a branch.
> 
> To get a copy of the branch, I do:
> 
> $ git checkout branches/2020Q4
> $ git branch
>    branches/2020Q2
>    branches/2020Q3
> * branches/2020Q4
>    master
> 
> Next, I want the tree as it existed at commit 46433baae934d92698422495b72f811839caa1a9
> 
> i.e. https://github.com/freebsd/freebsd-ports/commit/46433baae934d92698422495b72f811839caa1a9
> 
> My first attempt is
> 
> $ git checkout 46433baae934d92698422495b72f811839caa1a9
> Note: switching to '46433baae934d92698422495b72f811839caa1a9'.
> 
> You are in 'detached HEAD' state. You can look around, make experimental
> changes and commit them, and you can discard any commits you make in this
> state without impacting any branches by switching back to a branch.
> 
> If you want to create a new branch to retain commits you create, you may
> do so (now or later) by using -c with the switch command. Example:
> 
>    git switch -c <new-branch-name>
> 
> Or undo this operation with:
> 
>    git switch -
> 
> Turn off this advice by setting config variable advice.detachedHead to false
> 
> HEAD is now at 46433baae934 MFH: r555565
> 
> That "MFH: r555565' message indicates that I am at the right commit.
> 
> Is this a concern?
> 
> $ git branch
> * (HEAD detached at 46433baae934)
>    branches/2020Q2
>    branches/2020Q3
>    branches/2020Q4
>    master
> 
> 
> Am I doing this right?
> 
> Thank you
> 
>