worktree.c contains functions to work with and get information from
worktrees.  This introduction moves functions related to worktrees
from branch.c into worktree.c

Signed-off-by: Michael Rappazzo <rappazzo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Add a new function, find_shared_symref, which contains the heart of
die_if_checked_out, but works for any symref, not just HEAD.  Refactor
die_if_checked_out to use the same infrastructure as
find_shared_symref.

Soon, we will use find_shared_symref to protect notes merges in
worktrees.

Signed-off-by: David Turner <dturner@twopensource.com>
Reviewed-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-worktree currently conflates new branch creation, setting of HEAD in
the new wortkree, and worktree population into a single sub-invocation
of git-checkout. However, these operations will eventually be separated,
and git-worktree itself will need to be able to detect if the branch is
already checked out elsewhere, rather than relying upon git-branch to
make this determination, so publish die_if_checked_out().

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Like the "switched to..." message (which is already
suppressed by "-q"), this message is purely informational.
Let's silence it if the user asked us to be quiet.

This patch is slightly more than a one-liner, because we
have to teach create_branch to propagate the flag all the
way down to install_branch_config.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

* jn/branch-move-to-self:
  Allow checkout -B <current-branch> to update the current branch
  branch: allow a no-op "branch -M <current-branch> HEAD"

When on master, "git checkout -B master <commit>" is a more natural way to
say "git reset --keep <commit>", which was originally invented for the
exact purpose of moving to the named commit while keeping the local changes
around.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

This will be used by various callers that make use of the branch
description throughout the system, so that if we need to update
the implementation the callers do not have to be modified.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

The "git branch" command, while not in listing mode, calls create_branch()
even when the target branch already exists, and it does so even when it is
not interested in updating the value of the branch (i.e. the name of the
commit object that sits at the tip of the existing branch). This happens
when the command is run with "--set-upstream" option.

The earlier safety-measure to prevent "git branch -f $branch $commit" from
updating the currently checked out branch did not take it into account,
and we no longer can update the tracking information of the current branch.

Minimally fix this regression by telling the validation code if it is
called to really update the value of a potentially existing branch, or if
the caller merely is interested in updating auxiliary aspects of a branch.

Reported-and-Tested-by: Jay Soffian
Signed-off-by: Junio C Hamano <gitster@pobox.com>

"git branch -M <foo> <current-branch>" allows updating the current branch
which HEAD points, without the necessary house-keeping that git reset
normally does to make this operation sensible. It also leaves the reflog
in a confusing state (you would be warned when trying to read it).

"git checkout -B <current branch> <foo>" is also partly vulnerable to this
bug; due to inconsistent pre-flight checks it would perform half of its
task and then abort just before rewriting the branch. Again this
manifested itself as the index file getting out-of-sync with HEAD.

"git branch -f" already guarded against this problem, and aborts with
a fatal error.

Update "git branch -M", "git checkout -B" and "git branch -f" to share the
same check before allowing a branch to be created. These prevent you from
updating the current branch.

We considered suggesting the use of "git reset" in the failure message
but concluded that it was not possible to discern what the user was
actually trying to do.

Signed-off-by: Conrad Irwin <conrad.irwin@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

(Just like we did for documentation already)

In the process, we change "non-remote branch" to "branch outside the
refs/remotes/ hierarchy" to avoid the ugly "non-remote-tracking branch".
The new formulation actually corresponds to how the code detects this
case (i.e. prefixcmp(refname, "refs/remotes")).

Also, we use 'remote-tracking branch' in generated merge messages (by
merge an fmt-merge-msg).

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>