git log输出的差异--decorate :( HEAD - > master）vs（HEAD，master）

Question

When I get the log of a GIT repo:

git log --oneline --decorate --graph

the output is like this:

* 44025ed (HEAD -> master) second commit
* adf2dbb first commmit

In another repo, when I git log , I get:

* 435b61d (HEAD,master) bar
* 9773e52 foo

What is the difference between (HEAD -> master) and (HEAD,master)

Answer 1

The arrow points to the current branch

An arrow to the right of HEAD , in the output of git log --oneline --decorate --graph , indicates which branch (if any) is the current one.

* 44025ed (HEAD -> master) second commit

means that the symbolic reference HEAD currently points to the master branch; in other words, you are not in detached-HEAD state, and the current branch is master .

In contrast,

* 44025ed (HEAD, master) second commit

means that the symbolic reference HEAD does not currently point to any branch, but to a commit ( 44025ed ) directly; in other words, you are in detached-HEAD state. The master branch is only listed alongside HEAD because it happens to point to the same commit ( 44025ed ).

Some history

For information, this distinction was introduced in Git (2.4) shortly after Can git log --decorate unambiguously tell me whether the HEAD is detached? was asked on Stack Overflow.

A small experiment (to fix ideas)

$ mkdir decorate-test
$ cd decorate-test/
$ git init
Initialized empty Git repository in /xxxxxxx/decorate-test/.git/
$ touch README
$ git add README
$ git commit -m "Add README"
[master (root-commit) 50781c9] Add README
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 README
$ git log --oneline --decorate --graph
* 50781c9 (HEAD -> master) Add README
# Note the presence of the arrow in the output.

# Now, check out the commit directly to detach the HEAD:
$ git checkout 50781c9
Note: checking out '50781c9'.

You are in 'detached HEAD' state. You can look around, ...

HEAD is now at 50781c9... Add README
$ git log --oneline --decorate --graph
* 50781c9 (HEAD, master) Add README
# The arrow is gone!

# Check out master again to reattach the HEAD:
$ git checkout master
Switched to branch 'master'
$ git log --oneline --decorate --graph
* 50781c9 (HEAD -> master) Add README
# The arrow is back!