## Changes
A bug in the code that pulls the remote state could cause the local
state to be empty instead of a copy of the remote state. This happened
only if the local state was present and stale when compared to the
remote version.
We correctly checked for the state serial to see if the local state had
to be replaced but didn't seek back on the remote state before writing
it out. Because the staleness check would read the remote state in full,
copying from the same reader would immediately yield an EOF.
## Tests
* Unit tests for state pull and push mutators that rely on a mocked
filer.
* An integration test that deploys the same bundle from multiple paths,
triggering the staleness logic.
Both failed prior to the fix and now pass.
## Changes
Local file reads on Windows require the file handle to be closed after
using it. This commit includes an interface change to return an
`io.ReadCloser` from `Read` to accommodate this.
## Tests
The existing integration tests for the filer interface all pass.
## Changes
This PR:
1. Adds the export-dir command
2. Changes filer.Read to return an error if a user tries to read a
directory
3. Adds returning internal file structures from filer.Stat().Sys()
## Tests
Integration tests and manually
## Changes
This captures the recursive deletion of a directory tree in the filer interface.
Prompted by #433.
## Tests
Integration tests pass (ran the filer ones on AWS and Azure).
## Changes
The pattern `errors.Is(err, fs.ErrNotExist)` is common to check for an
error type.
Errors can implement `Is(error) bool` with a custom equivalence checker.
## Tests
New asserts all pass in the integration test.
Adds a DBFS implementation of the `filer.Filer` interface.
The integration tests are reused between the workspace filesystem and
DBFS implementations to ensure identical behavior.
Pieter Noordhuis
shreyas-goenka