Skip whole dir dockerignoring with warning

Fixes #7093
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
integration-cli: add more tests for BuildAddTar

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
integration-cli/TestBuildAddTar: generate context from test

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
integration-cli/TestBuildAddTar: embed Dockerfile

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
pkg/units: Using 'case' instead of trickled ifs

Seems the perfect case for 'case' ;).

Docker-DCO-1.1-Signed-off-by: Francisco Carriedo <fcarriedo@gmail.com> (github: fcarriedo)
pkg/units: Standardized supported sizes

May make sense that both `FromHumanSize()` and `RAMInBytes()` support
the same units. Added 'PB' to the RAMInBytes regex.

Also updated tests.

Note: int64 is overflowed on quantities >= EB

Docker-DCO-1.1-Signed-off-by: Francisco Carriedo <fcarriedo@gmail.com> (github: fcarriedo)
pkg/units: Refactor regexp.Compile to init()

No need to recompile a fixed regular expression each time the function
executes. Abstracting it to the `init()` method.

Docker-DCO-1.1-Signed-off-by: Francisco Carriedo <fcarriedo@gmail.com> (github: fcarriedo)
pkg/units: Compacted var declaration and initialization

No need to have two lines. The type is even explicit when type casting
to `float64(size)`

Docker-DCO-1.1-Signed-off-by: Francisco Carriedo <fcarriedo@gmail.com> (github: fcarriedo)
pkg/units: Moved 'units' out of function

No need to initialize every time the function executes since it works as
a catalog.

Docker-DCO-1.1-Signed-off-by: Francisco Carriedo <fcarriedo@gmail.com> (github: fcarriedo)
pkg/units: Refactored common code to single func

Both functions perform the same logic and they just vary on the base
multiplication units. We can refactor the common code into a single
place.

Docker-DCO-1.1-Signed-off-by: Francisco Carriedo <fcarriedo@gmail.com> (github: fcarriedo)
Test on building from GIT url

Also I added fake git server to utils
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
pkg/units: Updated `Compile()` to `MustCompile()`

We were doing exactly what `regexp.MustCompile()` already does.

Docker-DCO-1.1-Signed-off-by: fcarriedo <fcarriedo@gmail.com> (github: fcarriedo)
apache2 was looking for two other directories

/var/lock/apache2
/var/run/apache2
pkg/units: including suggestions and enhancements

Docker-DCO-1.1-Signed-off-by: fcarriedo <fcarriedo@gmail.com> (github: fcarriedo)
updated article to reflect changes in config; fixed hyperlinks #7243

Docker-DCO-1.1-Signed-off-by: Andrew Weiss <andrew.weiss@outlook.com> (github: anweiss)
address a few nits

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)
Merge pull request #7244 from anweiss/7243-dscarticle

Updated DSC article to reflect changes in config
Fix io.Reader ambiguity on EOF in progressreader

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)
Merge pull request #7238 from dericcrago/patch-1

apache2 was looking for two other directories
Merge pull request #7251 from tiborvass/fix-test-import-display

Fix test import display