Report the Go build info version when linker flags set none (closes #422)

A `go install` of a tag sets no linker flags, so the binary reported
`dev`. Version, commit and commit date that the linker flags leave
unset now come from the build info Go records. Go records a
pseudo-version for an untagged commit and a `+dirty` suffix for a
modified checkout; `IsDevVersion` now counts both as development
builds, using `golang.org/x/mod`.

Model: opus-5-5

README.md

@@ -1041,8 +1041,9 @@ is `git describe --tags --always --dirty`, which `script/version` runs for the
 A `docker build .` of a clone, with no build arguments, runs the same
 `git describe` (without `--dirty`) on the `.git` in its build context, so it
 stamps the same value for a clean commit; the build fails if the context carries
-`.git` and no version, commit or commit date comes out. `script/docker` and
-`script/cibuild` stamp `unknown` when they run outside a git checkout.
+`.git` and no version, commit or commit date comes out. `make` outside a git
+checkout and `docker build .` without `.git` both stamp `dev`. `script/docker`
+and `script/cibuild` stamp `unknown` when they run outside a git checkout.
 
 A binary built by plain `go install` or `go build` carries no stamped version.
 It reports the version Go recorded in it instead:
@@ -1056,13 +1057,21 @@ It reports the version Go recorded in it instead:
 tag `v1.0.0` produces `vaultik 1.0.0`, matching the archive name
 `vaultik_1.0.0_linux_amd64.tar.gz`. `goreleaser --snapshot` stamps
 `dev-<12 chars of the commit sha>` rather than inventing the next patch number.
-`vaultik version` calls a build a development build when its version is `dev`,
-`unknown`, `dev-<sha>`, the short commit sha, `<tag>-<N>-g<short sha>` or a Go
-pseudo-version, with or without `-dirty` or `+dirty`; only a plain tag, such as
-`v1.0.0` or `1.0.0`, is a release. If `script/version` cannot be run at all,
-`make` stops with an error instead of building an unversioned binary, and a
-binary that somehow carries an empty version string still reports itself as a
-development build.
+
+`vaultik version` calls a build a development build when its version is one of
+these:
+
+- `dev` or `unknown`.
+- `dev-<sha>`.
+- the short commit sha.
+- `<tag>-<N>-g<short sha>`.
+- a Go pseudo-version.
+- any version with a `-dirty` or `+dirty` suffix.
+
+Only a plain tag, such as `v1.0.0` or `1.0.0`, is a release. If `script/version`
+cannot be run at all, `make` stops with an error instead of building an
+unversioned binary, and a binary that somehow carries an empty version string
+still reports itself as a development build.
 
 ### cutting a release
 

internal/cli/entry.go

@@ -21,8 +21,8 @@ const shortCommitLen = 12
 const exitCodeInterrupted = 130
 
 // Entry is the main entry point for the CLI application.
-// It first takes the version, commit and commit date the linker flags
-// left unset from the Go build info (see globals.FromBuildInfo).
+// It first calls globals.UseBuildInfo, which fills in the version,
+// commit and commit date that the linker flags did not set.
 // It prints the startup banner to stderr (unless a banner-suppressing
 // flag is present in os.Args — see bannerSuppressedInArgs), executes the
 // root cobra command, and routes any returned error through the

internal/globals/globals.go

@@ -53,11 +53,13 @@ func UseBuildInfo() {
 		info, Version, Commit, CommitDate)
 }
 
-// FromBuildInfo returns version, commit and commitDate, with each one
-// the linker flags left unset taken from info. A `go install` of a tag
-// sets no linker flags, but Go records the tag as the main module's
-// version. Go records the commit and its time only when it builds from
-// a git checkout. The time is cut to a date, as the Makefile stamps it.
+// FromBuildInfo returns version, commit and commitDate. Each one that
+// still holds its default ("dev" or empty for the version, "unknown"
+// for the others) is replaced by the value Go recorded in info. A
+// `go install` of a tag sets no linker flags, but Go records the tag
+// as the main module's version. Go records the commit and its time
+// only when it builds from a git checkout. The time is cut to a date,
+// as the Makefile stamps it.
 func FromBuildInfo(
 	info *debug.BuildInfo, version, commit, commitDate string,
 ) (string, string, string) {