How to find the branch for a commit with JGit?

Question

I need to obtain the name of the branch that is associated with a specific commit using JGit. I used JGit to obtain the complete list of commit SHA's for a repository and now I need to know the name of the branch it belongs to.

Appreciate if someone can let me know how I can achieve this.

Just to mention only the tips (most recent commit) of branches are actually "associated" to the branch. For other commits, you can only guess by looking at the commits graph and history. — everag
– everag, Commented Nov 3, 2017 at 1:44

Rüdiger Herrmann · Accepted Answer · 2021-06-28 06:56:37Z

6

In Git, a commit does not belong to a branch. A commit is immutable, whereas branches can change their name as well as the commit they point to.

A commit is reachable from a branch (or tag, or other ref) if there is a branch that either directly points to the commit or to a successor of the commit.

In JGit the NameRevCommand can be used to find a branch, if any, that directly points to a commit. For example:

Map<ObjectId, String> map = git
  .nameRev()
  .addPrefix("refs/heads")
  .add(ObjectId.fromString("<SHA-1>"))
  .call();

The above snippet looks in the refs/heads namespace for a ref that points to the given commit. The returned map contains at most one entry where the key is the given commit id and the value denotes the branch which points to it.

edited Jun 28, 2021 at 6:56

answered Nov 3, 2017 at 6:18

Rüdiger Herrmann

21.1k11 gold badges66 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Antoniossss Over a year ago

What does it mean when given map is empty (just ran into such issue where "master" is expected

Rüdiger Herrmann Over a year ago

Seems that no ref was found that points to the commit id given with add. Does native Git return something?

Antoniossss Over a year ago

Didn't check (as it is temporary repository, fetched only single branch). I suspect this has something to do withe fact that I am actually using fetch_head - eg. I had to use "additionalRefs" to make log work as refs are empty in repository database. If i fetch with .all(), branch name is found (and no need to use additionalRefs.

Rüdiger Herrmann Over a year ago

You may try to use addRef with the Ref for FETCH_HEAD to have the command consider it.

ElpieKay · Accepted Answer · 2017-11-03 04:47:22Z

As the document says,

Class ListBranchCommand

ListBranchCommand setContains(String containsCommitish)

setContains

public ListBranchCommand setContains(String containsCommitish)

If this is set, only the branches that contain the specified commit-ish as an ancestor are returned.

Parameters:
containsCommitish - a commit ID or ref name

Returns:
this instance

Since:
3.4

This api is corresponding to git branch --contains <commit-ish>

You may also need this api if you'd like to list the remote branches (-r) or both the remote and local branches (-a),

setListMode

public ListBranchCommand setListMode(ListBranchCommand.ListMode listMode)

Parameters:
listMode - optional: corresponds to the -r/-a options; by default, only local branches will be listed

Returns:
this instance

Sample:

#list all the branches that "HEAD" belongs to.
try {
    Git git = Git.open(new File("D:/foo/.git"));
    List<Ref> refs = git.branchList().setContains("HEAD").setListMode(ListBranchCommand.ListMode.ALL).call();
    System.out.println(refs);
} catch (Exception e) {
    System.out.println(e);
}

Collectives™ on Stack Overflow

How to find the branch for a commit with JGit?

2 Answers 2

4 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related