Add builder dev report for 2017-07-17

Signed-off-by: Tonis Tiigi <[email protected]>

Author: tonistiigi

reports/builder/2017-07-17.md

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+# Development Report for July 17, 2017
+
+
+### BuildKit
+
+[Repo](https://github.com/moby/buildkit)
+[Proposal](https://github.com/moby/moby/issues/32925)
+
+Following features were added last week:
+
+#### Git source
+
+Source code from git repositories can now be accessed directly, similarly for images can be accessed, without the need to execute `git clone`. This has many performance and caching advantages. It accesses the remote repository using shallow fetches to only pull the required data and a uses a shared bare repository for intermediate cache between build invocations. The instruction cache for the git source is based on a commit hash and not string arguments. This means that you can always be sure that you are building the correct source and that you never build the same source twice.
+
+#### Containerd exporter
+
+Exporters are used for getting build artifacts out of buildkit. The first exporter that was implemented allows exposing the image to containerd so it can be run and pushed with `ctr` tool. `buildctl` has `--exporter` flag for specifying the exporter and `--exporter-opt` for custom values passed to the exporter. In the case of image exporter an image name can be specified.
+
+For example:
+
+```
+go run ./examples/buildkit2/buildkit.go | buildctl build --exporter image --exporter-opt name=docker.io/moby/buildkit:dev
+```
+
+Accessing from ctr/dist:
+
+```
+ctr --namespace buildkit images ls
+ctr --namespace buildkit rootfs unpack <manifest-sha>
+ctr --namespace buildkit run -t docker.io/moby/buildkit:dev id ash
+```
+
+#### Local source
+
+Buildkit now supports building from local sources. Snapshot of the local source files is created similarly to `docker build` build context. The implementation is based on the [incremental context send](https://github.com/moby/moby/pull/32677) feature in `docker-v17.07`. To use in `buildctl` the source definition needs to define a name for local endpoint, and `buildctl build` command provides a mapping from this name to a local directory with a `--local` flag.
+
+```
+go run ./examples/buildkit3/buildkit.go --local  | buildctl build --local buildkit-src=.
+``` 
+
+### Typed Dockerfile parsing
+
+[PR](https://github.com/moby/moby/pull/33492)
+
+Didn't manage to merge this PR yet. Still in code-review.
+
+
+### Feedback for `RUN --mount` / `COPY --chown`
+
+There was some new discussion around [`RUN --mount`](https://github.com/moby/moby/issues/32507) or [`COPY --chown`](https://github.com/moby/moby/issues/30110) feature. Currently, it seems that it may be best to try the shared cache capabilities described in `RUN --mount` in https://github.com/moby/buildkit first(it already supports the generic mounting capabilities). So to unblock the people waiting only on the file owner change features it may make sense to implement `COPY --chown` first. Another related candidate for `v17.08` release is https://github.com/moby/moby/issues/32816. 
+
+
+### Proposals for new Dockerfile features that need design feedback:
+
+[Add IMPORT/EXPORT commands to Dockerfile](https://github.com/moby/moby/issues/32100)
+
+[Add `DOCKEROS/DOCKERARCH` default ARG to Dockerfile](https://github.com/moby/moby/issues/32487)
+
+[Add support for `RUN --mount`](https://github.com/moby/moby/issues/32507)
+
+[DAG image builder](https://github.com/moby/moby/issues/32550)
+
+[Option to export the hash of the build context](https://github.com/moby/moby/issues/32963) (new)
+
+[Allow --cache-from=*](https://github.com/moby/moby/issues/33002#issuecomment-299041162) (new)
+
+[Provide advanced .dockeringore use-cases](https://github.com/moby/moby/issues/12886) [2](https://github.com/moby/moby/issues/12886#issuecomment-306247989)
+
+New: [RFC: Distributed BuildKit](https://github.com/moby/buildkit/issues/62)
+
+If you are interested in implementing any of them, leave a comment on the specific issues.
+
+### Builder features currently in code-review:
+
+[Fix shallow git clone in docker-build](https://github.com/moby/moby/pull/33704)
+
+### Backlog
+
+[Build secrets](https://github.com/moby/moby/issues/33343) has not got much traction. If you want this feature to become a reality, please make yourself heard.