I'm planning to study Firefox codebase. I tried to checkout repository as follows:
C:\mozilla\firefox> hg clone http://hg.mozilla.org/mozilla-central
destination directory: mozilla-central
requesting all changes
adding changesets
adding manifests
adding file changes
But it's now been 4-5 hrs. Nothing has been checked out yet. In #introduction IRC channel nobody is responding. Can I get some help from here?
It can take a while to download mozilla-central. For me it takes about 15-20 minutes, but if you do not have a reliable connection, or not a fast connection, it can be significantly slower.
By the way you should not expect to see anything in your repository other than the .hg subdirectory until the process is done. So it may seem hung, but it probably isn't.
There are work arounds for people in your situation:
If you have a poor network connection that is preventing 'hg clone' from completing, you may want to try downloading a bundle of the repository you're interested in (which, unlike 'hg clone', can be resumed when network problems interrupt the download).
Instructions and bundles are available here.
In general once you download the bundle you will do this:
hg init src
cd src
hg unbundle /path/to/your/repository.hg
Regarding your IRC experience:
On a side note this week is the Mozilla all-hands week where all mozilla employees, contractors, and some contributors get together. So your experiene on IRC was probably due to that. There is not as much presense on IRC during the Mozilla all-hands week.