# how.sh

takes a package name, a version, and a path.  mounts scripts for patching,
configuring, building, and installing the given version of the package at the
given path in read-only mode using either overlayfs or, if no package-specific
scripts were found, a bind mount.

dependencies: `shsort` and `vercmp`, as well as 'how-defaults' and 'how-pkgs'
repositories.  (see makefile.)

55 SLOC.

usage: how <package> <version> <path>

## package structure

if a package or version is not recognized, how.sh will bind-mount the `default`
directory in read-only mode at the requested path.  a package and version is
recognized based on the presence of a subdirectory in the `pkg` directory
matching the package name with a subdirectory whose name translates to a version
equal to or less than version of the package requested, or a subdirectory named
`default`.  the structure looks something like this:

    pkg/
    |-- <package>/
    |   |-- <version>/
    ...

`version` is matched using `vercmp`.  if `vercmp` has a format that matches the
package name, then that format is used to compare versions for the package.
otherwise, the default comparison function is used.

the version directories are sorted using `shsort` and `vercmp` and mounted as an
overlay filesystem with the lower versions being lower in the overlay and higher
versions being higher.  `default` package subdirectories are always one layer
above the `default` directory;  the `default` directory is always lowest.

## patches

multiple patches may be offered in a package.  by convention, patches are kept
in the `patches` subdirectory of the package root.  the default `patch` command
looks for a single combined patch, likely constructed by concatenating or
otherwise combining offered patches, under the filename `patch` in the package
root.