Add --exclude-from flag to sync commands

[anton-107]

Why

Exclude-from flag allows users to exclude file patterns from sync operations by providing a .gitignore -like file containing file patterns that should be excluded from sync

Usage:

$ databricks sync <SRC> <DEST> --exclude-from .databricksignore
$ databricks bundle sync --exclude-from .databricksignore

Tests

1. Added new acceptance tests
2. Added new unit test

[denik]

any reason to create these from script rather than create it in your worktree and commit with git?

[shreyas-goenka]

+1, lets serialize test fixture files.

[denik]

You could check different version of .databricksignore:

• refers to exact file (existing / missing(
• refers to exact directory (existing / missing)
• contains "**"

[denik]

This seems to duplicate functionality already present in go-gitignore

https://github.com/sabhiram/go-gitignore/blob/master/ignore.go#L182

// CompileIgnoreFile uses an ignore file as the input, parses the lines out of
// the file and invokes the CompileIgnoreLines method.
func CompileIgnoreFile(fpath string) (*GitIgnore, error) {

Pattern function strips comments and empty lines:
https://github.com/sabhiram/go-gitignore/blob/master/ignore.go#L77

	// Strip comments [Rule 2]
	if strings.HasPrefix(line, `#`) {
		return nil, false
	}

	// Trim string [Rule 3]
	// TODO: Handle [Rule 3], when the " " is escaped with a \
	line = strings.Trim(line, " ")

[shreyas-goenka]

+1, lets serialize test fixture files.

[shreyas-goenka]

Should this be an independent test instead of inlining it within bundle/sync? Makes it easier to reason about.

[pietern]

I expect --include-from to be almost identical, could you include it in this PR?

Separately, I would prefer if we not use .databricksignore even in our test files. It implies (to me) there are semantics associated with this file name, even though that's something we explicitly don't want.