Mercurial: get information about repositories without cloning them

Question

Few days ago I started experimenting with Mercurial, and everything went great, until I decided to try writting a small program, that gets the list of repositories and lists of changeset IDs for each repository from a remote server, allows the user to pick repository and changeset, clones it and updates to the chosen revision. This led to two questions:

1. Is there a way to get a list of repositories from server (besides parsing HTML)?
2. Is there a way to get information, such as tags, branches, etc. about one of the repositories, without actually cloning it first?

Answer 1

No, Mercurial is designed so that you need a local repository for almost all commands. The only built-in command that will give you information about a remote repository is hg id:

$ hg id https://bitbucket.org/aragost/javahg/
3b2711b26dbd

To get hold of more information you can sometimes exploit the raw template for hgweb:

$ wget -q -O - 'https://www.mercurial-scm.org/repo/hg/tags?style=raw' | head 
tip     a3a36bcf122e2ea4edbbe4ac44da59446cf0ee07
4.2.1   c850f0ed54c1d42f9aa079ad528f8127e5775217
4.2     bb96d4a497432722623ae60d9bc734a1e360179e
4.2-rc  616e788321cc4ae9975b7f0c54c849f36d82182b
4.1.3   77eaf9539499a1b8be259ffe7ada787d07857f80
4.1.2   ed5b25874d998ababb181a939dd37a16ea644435
4.1.1   25703b624d27e3917d978af56d6ad59331e0464a
4.1     e1526da1e6d84e03146151c9b6e6950fe9a83d7d
4.1-rc  a1dd2c0c479e0550040542e392e87bc91262517e
4.0.2   e69874dc1f4e142746ff3df91e678a09c6fc208c

That requires that the host is running the hgweb CGI script that comes with Mercurial. For a site like Bitbucket you would need to use their API.

Finally, if you can enable extensions on the remote repository, then it's possible to write an extension that exposes the information you want in a parsable format. I once wrote such an extension as a demo.