Add the etcd snap, in devmode.

etcd/README.md

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+# etcd snap
+
+This project creates a working snap of coreos etcd.
+This is a popular project, base of many distributed systems.
+etcd version on yakkety is 2.2.5, and upstream is now in 3.0.6. So snaps will
+be a nice way to deliver faster versions.
+
+It is using a custom plugin based on snapcraft's go plugin. This one sets up
+the go paths, and then calls the build command from the etcd repository.
+
+## Current state
+
+Working features:
+ - The binaries run in devmode.
+
+To do:
+ - More testing is needed to figure out the required interfaces for strict mode.
+
+Known issues:
+ - This can't be upstreamed yet because of bug https://bugs.launchpad.net/snapcraft/+bug/1615242

etcd/parts/plugins/x-etcd.py

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+"""This is a hacked version  of snapcraft's go plugin.
+
+It was modifyied to use etcd's build script.
+
+This plugin uses the common plugin keywords as well as those for "sources".
+For more information check the 'plugins' topic for the former and the
+'sources' topic for the latter.
+
+Additionally, this plugin uses the following plugin-specific keywords:
+
+    - go-importpath:
+      (string)
+      This entry tells the checked out `source` to live within a certain path
+      within `GOPATH`.
+"""
+
+import logging
+import os
+import shutil
+
+import snapcraft
+from snapcraft import common
+
+
+logger = logging.getLogger(__name__)
+
+
+class EtcdPlugin(snapcraft.BasePlugin):
+
+    @classmethod
+    def schema(cls):
+        schema = super().schema()
+        schema['properties']['go-importpath'] = {
+            'type': 'string',
+            'default': ''
+        }
+        # The import path must be specified.
+        schema['required'].append('go-importpath')
+
+        # Inform Snapcraft of the properties associated with pulling. If these
+        # change in the YAML Snapcraft will consider the pull step dirty.
+        schema['pull-properties'].append('go-importpath')
+
+        # Inform Snapcraft of the properties associated with building. If these
+        # change in the YAML Snapcraft will consider the build step dirty.
+        schema['build-properties'].extend(['source', 'go-importpath'])
+        return schema
+
+    def __init__(self, name, options, project):
+        super().__init__(name, options, project)
+        self.build_packages.append('golang-go')
+        self._gopath = os.path.join(self.partdir, 'go')
+        self._gopath_src = os.path.join(self._gopath, 'src')
+        self._gopath_bin = os.path.join(self._gopath, 'bin')
+
+    def pull(self):
+        # use -d to only download (build will happen later)
+        # use -t to also get the test-deps
+        # since we are not using -u the sources will stick to the
+        # original checkout.
+        super().pull()
+        os.makedirs(self._gopath_src, exist_ok=True)
+
+        go_package = self.options.go_importpath
+        go_package_path = os.path.join(self._gopath_src, go_package)
+        if os.path.islink(go_package_path):
+            os.unlink(go_package_path)
+        os.makedirs(os.path.dirname(go_package_path), exist_ok=True)
+        os.symlink(self.sourcedir, go_package_path)
+        self._run(['go', 'get', '-t', '-d', './{}/...'.format(go_package)])
+
+    def clean_pull(self):
+        super().clean_pull()
+
+        # Remove the gopath (if present)
+        if os.path.exists(self._gopath):
+            shutil.rmtree(self._gopath)
+
+    def build(self):
+        super().build()
+        build_command = os.path.join(
+            self.options.go_importpath, 'build')
+        self._run([build_command])
+
+        install_bin_path = os.path.join(self.installdir, 'bin')
+        os.makedirs(install_bin_path, exist_ok=True)
+        build_bin_path = os.path.join(self._gopath_src, 'bin')
+        for binary in os.listdir(build_bin_path):
+            binary_path = os.path.join(build_bin_path, binary)
+            shutil.copy2(binary_path, install_bin_path)
+
+    def clean_build(self):
+        super().clean_build()
+
+        if os.path.isdir(self._gopath_bin):
+            shutil.rmtree(self._gopath_bin)
+
+    def _run(self, cmd, **kwargs):
+        env = self._build_environment()
+        return self.run(cmd, cwd=self._gopath_src, env=env, **kwargs)
+
+    def _build_environment(self):
+        env = os.environ.copy()
+        env['GOPATH'] = self._gopath
+
+        include_paths = []
+        for root in [self.installdir, self.project.stage_dir]:
+            include_paths.extend(
+                common.get_library_paths(root, self.project.arch_triplet))
+
+        flags = common.combine_paths(include_paths, '-L', ' ')
+        env['CGO_LDFLAGS'] = '{} {} {}'.format(
+            env.get('CGO_LDFLAGS', ''), flags, env.get('LDFLAGS', ''))
+
+        return env

etcd/snapcraft.yaml

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+name: etcd
+version: v3.0.6
+summary: A distributed key-value store for shared configuration and service discovery.
+description: |
+  Etcd provides a key-value store and is implemented for high availability,
+  using the RAFT algorithm to deal with failover within the etcd cluster.
+  Popular in the Docker community as a shared store of small but important
+  pieces of common data in an application.
+confinement: devmode
+
+apps:
+  etcd:
+    command: bin/etcd
+  etcdctl:
+    command: bin/etcdctl
+
+parts:
+  etcd:
+    source: https://github.com/coreos/etcd.git
+    source-tag: v3.0.6
+    plugin: etcd
+    go-importpath: github.com/coreos/etcd