cmd/dist: delete special case for release branches without VERSION

findgoversion has some logic from before the go1 release that only
has effect when on a release branch without a VERSION file.

Starting with release-branch.go1 and the go1 tag a decade ago,
release branch have always had a VERSION file checked in.
(The commit that adds/updates the VERSION file is what is tagged.)

Since we have no need to support old branches like release-branch.r60,
and such scenarios don't come up in modern Go, delete it to simplify
this code a bit. Should the VERSION file situation change, we'd need
to rework this code anyway.

Fixes #42345.

Change-Id: I13f27babd37aaa5cec30fefde1b8e6ccce816461
Reviewed-on: https://go-review.googlesource.com/c/go/+/393954
Trust: Daniel Martí <[email protected]>
Trust: Dmitri Shuralyov <[email protected]>
Run-TryBot: Dmitri Shuralyov <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

src/cmd/dist/build.go

@@ -316,34 +316,6 @@ func chomp(s string) string {
  return strings.TrimRight(s, " \t\r\n")
 }
 
-func branchtag(branch string) (tag string, precise bool) {
- log := run(goroot, CheckExit, "git", "log", "--decorate=full", "--format=format:%d", "master.."+branch)
- tag = branch
- for row, line := range strings.Split(log, "\n") {
- // Each line is either blank, or looks like
- // (tag: refs/tags/go1.4rc2, refs/remotes/origin/release-branch.go1.4, refs/heads/release-branch.go1.4)
- // We need to find an element starting with refs/tags/.
- const s = " refs/tags/"
- i := strings.Index(line, s)
- if i < 0 {
- continue
- }
- // Trim off known prefix.
- line = line[i+len(s):]
- // The tag name ends at a comma or paren.
- j := strings.IndexAny(line, ",)")
- if j < 0 {
- continue // malformed line; ignore it
- }
- tag = line[:j]
- if row == 0 {
- precise = true // tag denotes HEAD
- }
- break
- }
- return
-}
-
 // findgoversion determines the Go version to use in the version string.
 func findgoversion() string {
  // The $GOROOT/VERSION file takes priority, for distributions
@@ -395,42 +367,26 @@ func findgoversion() string {
  }
 
  // Otherwise, use Git.
- // What is the current branch?
- branch := chomp(run(goroot, CheckExit, "git", "rev-parse", "--abbrev-ref", "HEAD"))
-
- // What are the tags along the current branch?
- tag := "devel"
- precise := false
-
- // If we're on a release branch, use the closest matching tag
- // that is on the release branch (and not on the master branch).
- if strings.HasPrefix(branch, "release-branch.") {
- tag, precise = branchtag(branch)
- }
-
- if !precise {
- // Tag does not point at HEAD; add 1.x base version, hash, and date to version.
- //
- // Note that we lightly parse internal/goversion/goversion.go to
- // obtain the base version. We can't just import the package,
- // because cmd/dist is built with a bootstrap GOROOT which could
- // be an entirely different version of Go, like 1.4. We assume
- // that the file contains "const Version = <Integer>".
-
- goversionSource := readfile(pathf("%s/src/internal/goversion/goversion.go", goroot))
- m := regexp.MustCompile(`(?m)^const Version = (\d+)`).FindStringSubmatch(goversionSource)
- if m == nil {
- fatalf("internal/goversion/goversion.go does not contain 'const Version = ...'")
- }
- tag += fmt.Sprintf(" go1.%s-", m[1])
-
- tag += chomp(run(goroot, CheckExit, "git", "log", "-n", "1", "--format=format:%h %cd", "HEAD"))
- }
+ //
+ // Include 1.x base version, hash, and date in the version.
+ //
+ // Note that we lightly parse internal/goversion/goversion.go to
+ // obtain the base version. We can't just import the package,
+ // because cmd/dist is built with a bootstrap GOROOT which could
+ // be an entirely different version of Go, like 1.4. We assume
+ // that the file contains "const Version = <Integer>".
+ goversionSource := readfile(pathf("%s/src/internal/goversion/goversion.go", goroot))
+ m := regexp.MustCompile(`(?m)^const Version = (\d+)`).FindStringSubmatch(goversionSource)
+ if m == nil {
+ fatalf("internal/goversion/goversion.go does not contain 'const Version = ...'")
+ }
+ version := fmt.Sprintf("devel go1.%s-", m[1])
+ version += chomp(run(goroot, CheckExit, "git", "log", "-n", "1", "--format=format:%h %cd", "HEAD"))
 
  // Cache version.
- writefile(tag, path, 0)
+ writefile(version, path, 0)
 
- return tag
+ return version
 }
 
 // isGitRepo reports whether the working directory is inside a Git repository.