what does git merge origin/master do?
git, git-merge
Solution
`git merge origin/master` can do one of two things (or error).
In the first case, it creates a new commit that has two parents: the current `HEAD`, and the commit pointed to by the ref `origin/master` (unless you're doing something funny, this is likely to be (the local pointer to) the branch named `master` on a remote named `origin`, though this is completely conventional).
In the second case, where there is no tree-level merge necessary, rather than creating a new commit, it updates the currently checked-out ref to point to the same commit as is pointed to by `origin/master`. (This is called a fast-forward merge -- git can be directed to either always or never do this when you merge through command-line flags).
It does not call `git commit` directly, which is a higher-level (porcelain in the git-parlance) command intended for users.
Calling `git merge master/original` will try and resolve `master/original` to a commit, which will almost certainly (again, unless you've done something deliberate) not be the same as `origin/master`. If you happen to have a remote named `master` that has a branch named `original`, it will create a new commit which has that as the second parent.
You may find `git help rev-parse` to be helpful in deciphering how git attempts to resolve ref names or other notations into commits.
Problem
After fetching from remote using `git fetch`, we need to use something like ``` git merge origin/master ``` I would like to know if this command also does `git commit` at the same time? Is the order `origin/master` important? Can I write `master/original`?