* removed packer.Cache and references since packer.Cache is never used except in the download step. The download step now uses the new func packer.CachePath(targetPath) for this, the behavior is the same.
* removed download code from packer that was reimplemented into the go-getter library: progress bar, http download restart, checksuming from file, skip already downloaded files, symlinking, make a download cancellable by context.
* on windows if packer is running without symlinking rights and we are getting a local file, the file will be copied instead to avoid errors.
* added unit tests for step_download that are now CI tested on windows, mac & linux.
* files are now downloaded under cache dir `sha1(filename + "?checksum=" + checksum) + file_extension`
* since the output dir is based on the source url and the checksum, when the checksum fails, the file is auto deleted.
* a download file is protected and locked by a file lock,
* updated docs
* updated go modules and vendors
Run now takes a context as well as a statebag. We'll assign the context
to the blank identifier to prevent namespace collisions. We'll let the
step authors opt-in to using the context.
`find . -iname "step_*.go" -exec gsed -i'' 's/func \(.*\)Run(/func \1Run(_ context.Context, /' {} \;`
[A recent breaking change upstream in Golang's crypto
library](e4e2799dd7)
has broken SSH connectivity for a few builders:
```
==> qemu: Waiting for SSH to become available...
2017/05/20 16:23:58 ui: ==> qemu: Waiting for SSH to become available...
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 [INFO] Attempting SSH connection...
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 reconnecting to TCP connection for SSH
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 handshaking with SSH
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 handshake error: ssh: must specify HostKeyCallback
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 [DEBUG] SSH handshake err: ssh: must specify HostKeyCallback
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 [INFO] Attempting SSH connection...
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 reconnecting to TCP connection for SSH
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 handshaking with SSH
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 handshake error: ssh: must specify HostKeyCallback
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 [DEBUG] SSH handshake err: ssh: must specify HostKeyCallback
```
Specifying HostKeyCallback as insecure should make things work again
and would make sense for packer's use case.
Adrien Delorme
Mikhail Ushanov
Megan Marsh
Matthew Hooker
Vijaya Bhaskar Reddy Kondreddi
Ali Bazlamit
JD Friedrikson
jasminSPC