Embed version info; print benchmark config (microsoft#1874)

Update how we set/read the version and commit information, so that it
can be set via writing to files instead of needing to update all `go
build` commands to add (or update) `-ldflags` with
`-X main.version=... -X manin.gitCommit=...".

Augment benchmark configuration with additional information, such as the
go version, number of CPUs available, start time, version, and git
branch and commit.

This allows standardizing the configuration data across different
benchmarking suites.

Benchmark config follow the benchmark raw data format:
https://go.googlesource.com/proposal/+/master/design/14313-benchmark-format.md

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

version/data/.gitignore

@@ -0,0 +1,4 @@
+# DO NOT MOVE: this file prevents `//go:embed data/*` from failing at build time
+BRANCH
+COMMIT
+VERSION

version/version.go

@@ -0,0 +1,41 @@
+package version
+
+import (
+ "embed"
+ "strings"
+)
+
+// Using `//go:embed data/VERSION` (similarly for `data/COMMIT` and `data/BRANCH`) will
+// fail at build time if the files don't exist, which will break existing build workflows.
+//
+// Alternatively, committing those files in git will cause problems as they will be constantly
+// updated and overwitten if devs update them locally and commit the changes.
+//
+// Therefore, we embed a (non-empty) directory and look up the files at run-time so builds
+// succeed regardless of whether the files are exist or not.
+// `data/.gitignore` is our fallback file, which keeps `data/` non-empty and prevents [embed]
+// from failing.
+
+// Using a dedicated `data` directory allows us to separate out what files to embed.
+// (Writing `//go:embed *` would include everything in this directory, including this file.)
+
+// See scripts/Set-VersionInfo.ps1 for an example of setting these values via files in data/.
+
+//go:embed data/*
+var data embed.FS
+
+var (
+ // Branch is the git branch the binary was built from.
+ Branch = readDataFile("BRANCH")
+
+ // Commit is the git commit the binary was built from.
+ Commit = readDataFile("COMMIT")
+
+ // Version is the complete semver.
+ Version = readDataFile("VERSION")
+)
+
+func readDataFile(f string) string {
+ b, _ := data.ReadFile("data/" + f)
+ return strings.TrimSpace(string(b))
+}