mkosi: Keep mkosi.default out of the repository.

Defaulting to fedora makes it a pain to override mkosi.default
point to one of the other mkosi settings files. Instead, have
every developer manually add the symlink to his distro
of choice and don't commit the symlink to the repository by
putting it in the .gitignore.

.gitignore

@@ -35,4 +35,5 @@ __pycache__/
 /.mkosi-*
 /mkosi.builddir/
 /mkosi.output/
+/mkosi.default
 /tags

docs/HACKING.md

@@ -36,9 +36,12 @@ building clean OS images from an upstream distribution in combination with a
 fresh build of the project in the local working directory. To make use of this,
 please acquire `mkosi` from https://github.com/systemd/mkosi first, unless your
 distribution has packaged it already and you can get it from there. After the
-tool is installed it is sufficient to type `mkosi` in the systemd project
-directory to generate a disk image `image.raw` you can boot either in
-`systemd-nspawn` or in an UEFI-capable VM:
+tool is installed, symlink the settings file for your distribution of choice from
+.mkosi/ to mkosi.default in the project root directory (note that the package
+manager for this distro needs to be installed on your host system). After doing
+that, it is sufficient to type `mkosi` in the systemd project directory to
+generate a disk image `image.raw` you can boot either in `systemd-nspawn` or in
+an UEFI-capable VM:
 
 ```
 # systemd-nspawn -bi image.raw
@@ -80,6 +83,7 @@ $ vim src/core/main.c                  # or wherever you'd like to make your cha
 $ meson build                             # configure the build
 $ ninja -C build                          # build it locally, see if everything compiles fine
 $ ninja -C build test                     # run some simple regression tests
+$ ln -s .mkosi/mkosi.fedora mkosi.default # Configure mkosi to build a fedora image
 $ (umask 077; echo 123 > mkosi.rootpw)    # set root password used by mkosi
 $ sudo mkosi                              # build a test image
 $ sudo systemd-nspawn -bi image.raw       # boot up the test image

mkosi.default

@@ -1 +0,0 @@
-.mkosi/mkosi.fedora