Also make the repo action button font size text-sm.

drive-by fixes:
- make the edit icon for repo-descriptions more compact
- do not double-pad rendered blob contents

Turns out we were accidentally using the destination knot as the
sourceUrl, and git was understandably annoyed. This also improves the
error checking when fetching the existingRepo from the database to
verify the forkName won't clash.

Forces smaller viewports to w-full all comments; on bigger screens we set a max-width of 3/5.

Thanks @dvjn.dev!

Also sets up a pages/markup package with extensible rendering for future markup languages that we may support.
We may also want an interface or something for markup.RenderMarkdown (maybe just markup.Render), but don't have to bother with that now.

timeline events in profiles are grouped by month (each month is a card) and by type (repos, issues and pulls).

We should make this optional...

resubmit checks are valid only for users that are logged in

it is set to `/home/git/repositories` everywhere else (volume mounting, keyfetch config, etc) inside the docker directory.

without this, knotserver uses the default value "/home/git" which means it is out of sync with everywhere else.

the existing diff calculation approach directly compares branches, this forces linear history for merge. this patch updates the diff logic to use the common ancestor commit to calculate diffs.

```
P Q
o---o topic
/
/
o---o---o---o master
A X Y
```

when diffing topic and master directly with difftree (Q and Y), the commits introduced in master since the creation of the branch, namely, X and Y, are considered "removed" from the generated patch. however, when diffing with the common ancestor A, only changes introduced by P and Q are included in the produced patch.

this calculation can be retired in favor of format-patch soon enough (i think).

this capability has existed in knots since the first release

This container embeds everything in one container:
- knotserver
- repoguard
- keyfetch
- sshd server

To supervise knot and sshd servers I decided to use well known s6-overlay. After first launch it execline script will create host keys. knotserver runs under git, sshd under root.

this should be overridden last

- proper tabindex for login page form
- overflow for handles in profile page

no idea why 5 wont suffice, but luckily bigger numbers exist

fix bug where forked repo was created twice

unless a branch is updated, resubmit will remain disabled; and when
there are changes added to the branch, a hint is supplied.

Added two additional options:
- stateDir: controls where the knotserver's state should be stored
(defaults to `/home/git` to maintain compatibility with previous configs)
- openFirewall: decides if we should open port 22 for ssh
(defaults to true to maintain compatibility with previous configs)

Made use of config options that weren't being used

Changed the `gitUser` to be a system user instead of a normal user.
This is purely cosmetic and pretty much just keeps the UID and GID
below 1000. If the user and group were already made, NixOS won't
change them so this shouldn't have the possibility of breaking any
existing setups but if the UID and GID are changing, the activation
script that creates the directories should update the owner of all the
state files.

Add short-hand for `config.services.tangled-knotserver`
Instead of typing `config.services.tangled-knotserver` we can now use
`cfg` to refer to the module's options.

closes issue #52

Fix stdin piping to git-upload-pack. I think we were closing the pipe
too soon previously, resulting in the 'fatal: remote end hung up
unexpectedly' error. Probably went unnoticed for smaller repos.

Also fix a bunch of misc. bugs in with superfluous http header writes
and the gzip reader being shadowed.