Adding git subtree from a branch

Question

I'm trying to add a repo (called cow) to my project using git subtree add. In particular, I'd like to add the branch stable (which is not the master branch). I tried:

git subtree add -P cow https://github.com/geoffryan/cow.git stable

But this returned the error

'stable' does not refer to a commit.

I also tried:

git subtree add -P cow https://github.com/geoffryan/cow.git cow/stable
'cow/stable' does not refer to a commit.

And:

git subtree add -P cow https://github.com/geoffryan/cow.git ca26d248a12c21264e32a2c212381cafb578c9fb
'ca26d248a12c21264e32a2c212381cafb578c9fb' does not refer to a commit.

The hash was that for the latest commit in the stable branch. The examples of use I've seen online all use master for the commit, is it possible to use subtree add on a non-master branch?

Answer 1

This seems to work

$ git remote add cow https://github.com/geoffryan/cow.git
$ git fetch cow
$ git subtree add -P cow cow/stable
Added dir 'cow'

I don't understand how to use directly the command with the repository part.

Answer 2

I encounter a similar problem. However, gipi's solution doesn't work for me. Oddly, when I add master branch everythins is fine, but when I want to add other branches, it returns

fatal: Couldn't find remote ref xxx/yyy
Unexpected end of command stream

So I tried another way:

mkdir tmp
cd tmp
git init
git clone url_for_xxx.git yyy

And subtree add from that temp rep's master branch:

git subtree add -P yyy /path/to/tmp/ master