I know it is not possible to create Mercurial repositories remotely using HTTP(S), for instance:
$ hg init https://host.org/repos/project
or
$ hg clone /path/to/local/project https://host.org/repos/project
But, what's the reason? Security issues? No need for it? Simply because nobody has implemented it yet?
Rationale for this question: In my company we share most resources via HTTPS, i.e. access permissions are managed by Apache only and regular users cannot login via SSH on the server. That's just perfect as long as repositories need to be served only (for that purpose we are happy with hgwebdir.cgi). However, we also want to allow the remote creation of repos, without the need to maintain additional/patched scripts on the server and extra tools on clients.
To be clear: This question does not ask for solutions to our particular problem but for the reason why Mercurial does not support this feature itself.
UPDATE
Here's a more technical description of the situation I'm thinking of. Supposed hgwebdir.cgi serves a collection of repositories in /path/to/repos at https://.../repos (with pushing enabled). Every user allowed to access this URL (as configured in Apache) may pull and push changesets, effectively this means that hgwebdir.cgi (and thus hg) edits and creates files below /path/to/repos. Now, what's the barrier in letting hgwebdir.cgi also create new repositories below /path/to/repos?
I think the reason is that adding support for creating repositories will bring in a fair amount of baggage:
if you can create repositories you would expect to be able to delete them. While that might seem simple, it would be a big step away from the safe manner in which Mercurial normally works -- there is no destructive commands in standard Mercurial.
people would also want to edit the .hg/hgrc files to set the description and contact information -- standard Mercurial never changes the config files, so this would again be a new thing.
people would also want to manage users' access to the new repositories -- this means editing .htaccess files or the equivalent for other webservers.
... and so on. Implementing this "little" feature will open up for a lot of extra feature requests and we only have a few Mercurial developers that are also sawy web developers.
However, there is now an excellent open source solution: Kallithea gives you a "mini-Bitbucket" that you can deploy on your own server. It will do all of the above. I would install that on my server if I needed something more powerful than plain hgweb.cgi. It supports both Mercurial and Git.
As far as I know, none of the SCM alternatives allow the creation of remote repositories natively. SVN, CVS, Git, et al.
That's usually the job of a hosting provider: SourceForge, Google Code, BitBucket. All of them implement the repository creation on top of their authetication infrastructure.
For example, Debian's Mercurial hosting is limited to Debian Developers, and to create a new repository you need to login via SSH to the server and create the repository on your local home folder, much like Apache's public_html directory.
Various answers (including your own) give some pretty good reasons why the functionality isn't there (separation of concerns mostly), but if you really want to add it you could do so with just a line or two of shell. Here's a hideously unsafe example I gave quite a while ago showing how to add that funcionality in high trust environments: Remote Repository Creation in Mercurial over HTTP
