pull creates confusing remote branches

[kasal]

To reproduce:

1. clone a repo (e.g., file://...)
2. create a local branch (e.g., "foo") and check it out
3. Pull, accepting the defaults offered by the dialog

Actual result:
this creates a new remote branch corresponding to origin/HEAD,
e.g., refs/remotes/origin/foo
(You need prune them using "git remote prune origin" or using the remotes dialog.)

Expected result:

• Error: this is not a remote tracking branch.

Explanation:
This confuses people. The worst problem is there "origin/foo" is displayed, the remote does not actually exist.

Code:
The command issued is:
"C:\Program Files (x86)\Git\bin\git.exe" pull --progress "origin" :refs/remotes/origin/foo

Fix:
I believe that if no remote branch is explicitly selected in the dialog, the second parameter should be omitted. (This is already so if the current branch is remote-tracking.)
This would lead to the error explaining that "pull" is to be used mainly with remote-tracking branches.

[pmme]

This appears to be closely related to: #2142

[kasal]

Indeed, this was a duplicate, thank you for the reference.
Sorry that I wasn't able to test the current master...