You're going to pull some changes, but oops, you're not up to date:

> git fetch origin
> git pull origin master
From ssh://gitosis@example.com:22/projectname
 * branch            master     -> FETCH_HEAD
Updating a030c3a..ee25213
error: Entry 'filename.c' not uptodate. Cannot merge.

So you get up-to-date and try again, but have a conflict:

> git add filename.c
> git commit -m "made some wild and crazy changes"
From ssh://gitosis@example.com:22/projectname
 * branch            master     -> FETCH_HEAD
Auto-merging filename.c
CONFLICT (content): Merge conflict in filename.c
Automatic merge failed; fix conflicts and then commit the result.

So you decide to take a look at the changes:

> git mergetool

Oh me, oh my, upstream changed some things, but just to use my changes.... no... their changes...

> git checkout --ours filename.c
> git checkout --theirs filename.c
> git add filename.c
> git commit -m "using theirs"

And then we try a final time

> git pull origin master
From ssh://gitosis@example.com:22/projectname
 * branch            master     -> FETCH_HEAD
Already up-to-date.

Ta-da!