Added copyTree function and replaced the template copyFiles calls

[rgee0]

Signed-off-by: rgee0 [email protected]

Main Change:
Created a copyTree function to address issue#18.
The function takes a similar approach to copyFiles but on finding a folder creates an equivalent folder in the build dir and then calls itself, this time passing in the source folder and newly created target folder. This means that all files and folder to n-levels will be copied.
A helper function has also been created; pathExists() is used within copyTree to try to offset errors where the destination may already exist.
Finally, replaced the two copyFile calls for the template folders with a single call to copyTree and amended the TODO comment accordingly.

Test:
Created 10 levels of files and folders beneath a template folder
Ran ./faas-cli -action build -yaml ./samples.yml
Confirmed that the images built successfully.
Confirmed that the expected files and folders were extant in the build folder following completion of build.

Other small edits:
Standardised some of the messages returned to the user.
Some diffs being shown are a result of vscode re-formatting.

Misc:
Used git commit -s as per the contribution guide

[alexellis]

Thanks for this!

[alexellis]

Looks good. I wonder if we can keep the name copyFiles or something similar?

[rgee0]

I left copyFiles in for situations where only files needed copying, so we have a choice:

Assume every copy will need to do the whole tree from its start path. Remove copyFiles and rename copyTreeTo copyFiles.

Leave copyFiles for situations where only the path's files require to be copied. Rename copyTree To copyFilesTree.

[alexellis]

I was thinking a single function - either copyFiles which is always depth-recursive or copyFiles plus a flag recursive for when you don't want to go down the file-structure?

[rgee0]

Cool. We'll go with the additional param since that allows us greater control

[alexellis]

Thanks for this 💥