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JGit: How to get branch from a commit id [message #784829]

Sat, 28 January 2012 02:45

kamalakannan muralidharan

Messages: 3
Registered: January 2012

Junior Member

Hi

I want the code snippet (using JGit), to get the branch on which a commit was made.
This code is needed because when a checkout happens from a commit ID, the normal api of getbranch returns the commit id (because it will be detached No_branch state). so i need to find the actual branch from commit ID

Regards
Kamal

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Re: JGit: How to get branch from a commit id [message #786302 is a reply to message #784829]

Mon, 30 January 2012 08:43

Christian Halstrick

Messages: 18
Registered: July 2009

Junior Member

I don't think that Git can tell that always. With the help of reflog you may find out for locally created versions (only for a certain period of time until old reflog entries are deleted), but not for versions which you have received from remote. With which native git commands would you get this information?

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Re: JGit: How to get branch from a commit id [message #786758 is a reply to message #786302]

Mon, 30 January 2012 19:49

kamalakannan muralidharan

Messages: 3
Registered: January 2012

Junior Member

Thanks for the info.

git branch --contains <commit>

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Re: JGit: How to get branch from a commit id [message #786850 is a reply to message #786758]

Mon, 30 January 2012 22:05

Christian Halstrick

Messages: 274
Registered: July 2009

Senior Member

'git branch --contains <commit>' will report every branch which contains this commit. In the standard push/fetch workflows for all commits you get from remote only "origin/master" is reported. And even for local commits: Imagine you have merged your feature branch back to master. Then this command will report also the master branch and all feature branches created after merging. Git simply doesn't store for a revision on which branch it was created.

After these warnings: a rough implementation of "git branch --conttains <commit>" could look like this:

		Repository repo = new FileRepository(args[0]);
		RevWalk walk = new RevWalk(repo);
		RevCommit commit = walk.parseCommit(repo.resolve(args[1] + "^0"));
		for (Map.Entry<String, Ref> e : repo.getAllRefs().entrySet())
			if (e.getKey().startsWith(Constants.R_HEADS))
				if (walk.isMergedInto(commit,
						walk.parseCommit(e.getValue().getObjectId())))
					System.out.println("Ref " + e.getValue().getName()
							+ " contains commit " + commit);

Ciao
Chris

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