Re: Git checkout multiple options issue

[Junio C Hamano <gitster@pobox.com>]

Kevin Daudt <me@ikke.info> writes:

> On Mon, Jan 28, 2019 at 10:20:02AM -0500, Randall S. Becker wrote:
>> On January 28, 2019 9:25, COLLOMB Joris wrote:
>> ...
>> > git checkout -f -b "branch_name"
>> > gives me " Fatal: A branch named 'branch_name' already exists."
>> 
>> Once the branch is created, you can't force its creation, because it is
>> already created. Just
>> 
>> git checkout "branch_name"
>> 
>> is sufficient at this point. git is correct to complain that you are trying
>> to create a branch that already exists.
>
> git checkout -B exists, which does exactly that: force create a branch
> at a new positon if it already exists.

Correct.

"git checkout -b/-B" is for lazy people to perform two things,
i.e. "creating a branch" and "checking the branch out", at the same
time.

If we did not allow "git checkout -b newbranch othercommit" and only
allowed "git checkout -b newbranch", i.e. to start a branch at the
current HEAD, then we could make "git checkout -f -b newbranch" to
mean "git checkout -B newbranch", because creating a branch at HEAD
and checking it out will not have a risk of overwriting local
changes, i.e. no need to force the "checking the branch out" part,
so the "--force" option can only mean "force creating the branch".

But because the new branch can begin at the commit whose tree
differs at a path that has local modifications, there needs a way to
tell the command which part, either "creating a branch" or "checking
the branch out", is being forced.  Hence, "-f" tells the "checking
out the branch" part to do the forcing (e.g. allowing local changes
to be overwritten), and "creating a branch" part is told to force
with the distinction between "-b" and "-B".