$ mkdir remote_repo1
$ cd remote_repo1/
$ git init .
Initialized empty Git repository in /tmp/remote_repo1/.git/
$ echo "repo1" > myfile
$ git add myfile 
$ git commit myfile -m "init"
[master (root-commit) 043d3c6] init
 1 file changed, 1 insertion(+)
 create mode 100644 myfile

$ cd ../
$ mkdir remote_repo2
$ cd remote_repo2/
$ git init .
Initialized empty Git repository in /tmp/remote_repo2/.git/
$ echo "repo2" > myfile
$ git add myfile 
$ git commit myfile -m "init"
[master (root-commit) 5c329bf] init
 1 file changed, 1 insertion(+)
 create mode 100644 myfile

$ cd ../
$ tree remote_repo1 remote_repo2/
remote_repo1
└── myfile
remote_repo2/
└── myfile

$ git clone remote_repo1/ local_repo
Cloning into 'local_repo'...
done.
$ cd local_repo/
$ git remote -v
origin    /tmp/remote_repo1/ (fetch)
origin    /tmp/remote_repo1/ (push)

$ git remote add repo2 /tmp/remote_repo2/
$ git remote -v
origin    /tmp/remote_repo1/ (fetch)
origin    /tmp/remote_repo1/ (push)
repo2 /tmp/remote_repo2/ (fetch)
repo2 /tmp/remote_repo2/ (push)

$ git fetch repo2
warning: no common commits
remote: Counting objects: 3, done.
remote: Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
From /tmp/remote_repo2
 * [new branch]      master     -> repo2/master

$ git checkout -b local_repo2 repo2/master
Branch local_repo2 set up to track remote branch master from repo2.
Switched to a new branch 'local_repo2'

$ git branch -a
* local_repo2
  master
  remotes/origin/HEAD -> origin/master
  remotes/origin/master
  remotes/repo2/master

$ git diff master 
diff --git a/myfile b/myfile
index 464d9cd..27d38ae 100644
 a/myfile
+++ b/myfile
@@ -1 +1 @@
-repo1
+repo2

$ git merge master 
Auto-merging myfile
CONFLICT (add/add): Merge conflict in myfile
Automatic merge failed; fix conflicts and then commit the result.

$ git status 
On branch local_repo2
Your branch is up-to-date with 'repo2/master'.
You have unmerged paths.
  (fix conflicts and run "git commit")

Unmerged paths:
  (use "git add <file>..." to mark resolution)

  both added:      myfile

no changes added to commit (use "git add" and/or "git commit -a")

$ cat myfile 
<<<<<<< HEAD
repo2
=======
repo1
>>>>>>> master
$ echo shut-up > myfile 

$ git add myfile 

$ git commit -m "Overwrite myfile"
[local_repo2 a76c0a6] Overwrite myfile

$ git push repo2 
warning: push.default is unset; its implicit value has changed in
Git 2.0 from 'matching' to 'simple'. To squelch this message
and maintain the traditional behavior, use:

  git config --global push.default matching

To squelch this message and adopt the new behavior now, use:

  git config --global push.default simple

When push.default is set to 'matching', git will push local branches
to the remote branches that already exist with the same name.

Since Git 2.0, Git defaults to the more conservative 'simple'
behavior, which only pushes the current branch to the corresponding
remote branch that 'git pull' uses to update the current branch.

See 'git help config' and search for 'push.default' for further information.
(the 'simple' mode was introduced in Git 1.7.11. Use the similar mode
'current' instead of 'simple' if you sometimes use older versions of Git)

fatal: The upstream branch of your current branch does not match
the name of your current branch.  To push to the upstream branch
on the remote, use

    git push repo2 HEAD:master

To push to the branch of the same name on the remote, use

    git push repo2 local_repo2

To choose either option permanently, see push.default in 'git help config'.