"No commit specified and merge.defaultToUpstream not set"

Question

As a new git user, who is an expert with SVN and CVS, I am struggling to get the most basic of git functions to work.

I'm using a shared repo at assembla.com

I created a local clone, and added a file:

$ git clone repository-url $ echo "hello" > ha.txt $ git add -A $ git commit -a -m "haha" $ git push 

NOTE: at this point I got "No refs in common and none specified; doing nothing" error. After some hours googling, I found the solution was to type this

$ git push origin master 

Then I went onto another computer, modified the file, and commit-ed it (surprisingly, I didn't need to do the git push origin magic). Then I back to the main computer, modified it again, so I could see how merge works.

$ git fetch $ git merge 

Now I get the error:

fatal: No commit specified and merge.defaultToUpstream not set.

Looking at the man page for "git merge", you have to specify something like this:

$ git merge [< commit >..] 

The problem is, I cant find out what < commit > means, and what it should be. E.g. should it be a file, a repo, a message, a version?

I have not created a branch - I'm just working on the "head" or master as I think git calls it

Unfortunately, google is not much help on this one. The man pages seem to expect you to know what a < refspec >, < commit > and origin are.

Any help on this noob problem appreciated.

Answer 1

Usually you do not invoke git merge without arguments (at least I don't know anyone who does). If you want that merge defaults to the tracking branch, you need to set merge.defaultToUpstream to true: git config merge.defaultToUpstream true. Your master branch has to track origin/master in this case: git branch --set-upstream master origin/master. This is done automagically if origin/master was already present when you cloned.

Personally, I do git fetch and then git merge origin/master or git pull if I have no local commits.

Edit: As VonC mentioned merge.defaultToUpstream defaults to true since Git 2.0.

Answer 2

Note: if your master branch is already tracking origin/master (you can see that with git branch -avvv, or a longer alias), then a git merge will not display anymore:

fatal: No commit specified and merge.defaultToUpstream not set. 

The next Git 2.à.x (Q3 2014) will remove that error message:
see commit a01f7f2 by Felipe Contreras (felipec):

merge: enable defaulttoupstream by default

There's no point in this:

% git merge fatal: No commit specified and merge.defaultToUpstream not set. 

We know the most likely scenario is that the user wants to merge the upstream, and if not, he can set merge.defaultToUpstream to false.

That means you won't need anymore to do a:

git config merge.defaultToUpstream true 

As noted with Git 2.33 (Q3 2021): Defaults to true.

See commit 8603c41 (07 Jun 2021) by Felipe Contreras (felipec).
^{(Merged by Junio C Hamano -- gitster -- in commit 11fac26, 08 Jul 2021)
Signed-off-by: Felipe Contreras}