commit c2626a8270 replaced the use of
github.com/docker/docker/pkg/homedir with Golang's os.UserHomeDir().
This change was partially reverted in 7a279af43d
to account for situations where `$HOME` is not set.
In situations where no configuration file is present in `~/.config/`, the CLI
falls back to looking for the (deprecated) `~/.dockercfg` configuration file,
which was still using `os.UserHomeDir()`, which produces an error/warning if
`$HOME` is not set.
This patch introduces a helper function and a global variable to get the user's
home-directory. The global variable is used to prevent repeatedly looking up
the user's information (which, depending on the setup can be a costly operation).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
c85a37dbb4