cmd/go: implement accurate pseudo-versions for Mercurial

This is CL 124515 (which only did Git) but for Mercurial,
quite a few years late. I'm not sure why we didn't do it
at the time - probably Mercurial blindness. Do it now.

Change-Id: I28f448a19143f7ce3de337cd1891bae86023b499
Reviewed-on: https://go-review.googlesource.com/c/go/+/718502
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Michael Matloob <matloob@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/go/internal/modfetch/codehost/git.go

@@ -794,15 +794,18 @@ func (r *gitRepo) RecentTag(ctx context.Context, rev, prefix string, allowed fun
 	// There are plausible tags, but we don't know if rev is a descendent of any of them.
 	// Fetch the history to find out.
 
+	// Note: do not use defer unlock, because describe calls allowed,
+	// which uses retracted, which calls ReadFile, which may end up
+	// back at a method that acquires r.mu.
 	unlock, err := r.mu.Lock()
 	if err != nil {
 		return "", err
 	}
-	defer unlock()
-
 	if err := r.fetchRefsLocked(ctx); err != nil {
+		unlock()
 		return "", err
 	}
+	unlock()
 
 	// If we've reached this point, we have all of the commits that are reachable
 	// from all heads and tags.

src/cmd/go/internal/modfetch/codehost/vcs.go

@@ -25,6 +25,8 @@ import (
 	"cmd/go/internal/lockedfile"
 	"cmd/go/internal/str"
 	"cmd/internal/par"
+
+	"golang.org/x/mod/semver"
 )
 
 // A VCSError indicates an error using a version control system.
@@ -167,6 +169,8 @@ type vcsCmd struct {
 	parseStat          func(rev, out string) (*RevInfo, error)           // func to parse output of statLocal
 	fetch              []string                                          // cmd to fetch everything from remote
 	latest             string                                            // name of latest commit on remote (tip, HEAD, etc)
+	descendsFrom       func(rev, tag string) []string                    // cmd to check whether rev descends from tag
+	recentTags         func(rev string) []string                         // cmd to print tag ancestors of rev
 	readFile           func(rev, file, remote string) []string           // cmd to read rev's file
 	readZip            func(rev, subdir, remote, target string) []string // cmd to read rev's subdir as zip file
 
@@ -217,6 +221,12 @@ var vcsCmds = map[string]*vcsCmd{
 		parseStat: hgParseStat,
 		fetch:     []string{"hg", "pull", "-f"},
 		latest:    "tip",
+		descendsFrom: func(rev, tag string) []string {
+			return []string{"hg", "log", "-r", "ancestors(" + rev + ") and " + tag}
+		},
+		recentTags: func(rev string) []string {
+			return []string{"hg", "log", "-r", "ancestors(" + rev + ") and tag()", "--template", "{tags}\n"}
+		},
 		readFile: func(rev, file, remote string) []string {
 			return []string{"hg", "cat", "-r", rev, file}
 		},
@@ -558,16 +568,37 @@ func (r *vcsRepo) ReadFile(ctx context.Context, rev, file string, maxSize int64)
 }
 
 func (r *vcsRepo) RecentTag(ctx context.Context, rev, prefix string, allowed func(string) bool) (tag string, err error) {
-	// We don't technically need to lock here since we're returning an error
+	// Only lock for the subprocess execution, not for the tag scan.
-	// unconditionally, but doing so anyway will help to avoid baking in
+	// allowed may call other methods that acquire the lock.
-	// lock-inversion bugs.
 	unlock, err := r.mu.Lock()
 	if err != nil {
 		return "", err
 	}
-	defer unlock()
 
-	return "", vcsErrorf("vcs %s: RecentTag: %w", r.cmd.vcs, errors.ErrUnsupported)
+	if r.cmd.recentTags == nil {
+		unlock()
+		return "", vcsErrorf("vcs %s: RecentTag: %w", r.cmd.vcs, errors.ErrUnsupported)
+	}
+	out, err := Run(ctx, r.dir, r.cmd.recentTags(rev))
+	unlock()
+	if err != nil {
+		return "", err
+	}
+
+	highest := ""
+	for _, tag := range strings.Fields(string(out)) {
+		if !strings.HasPrefix(tag, prefix) || !allowed(tag) {
+			continue
+		}
+		semtag := tag[len(prefix):]
+		if semver.Compare(semtag, highest) > 0 {
+			highest = semtag
+		}
+	}
+	if highest != "" {
+		return prefix + highest, nil
+	}
+	return "", nil
 }
 
 func (r *vcsRepo) DescendsFrom(ctx context.Context, rev, tag string) (bool, error) {
@@ -577,7 +608,15 @@ func (r *vcsRepo) DescendsFrom(ctx context.Context, rev, tag string) (bool, erro
 	}
 	defer unlock()
 
-	return false, vcsErrorf("vcs %s: DescendsFrom: %w", r.cmd.vcs, errors.ErrUnsupported)
+	if r.cmd.descendsFrom == nil {
+		return false, vcsErrorf("vcs %s: DescendsFrom: %w", r.cmd.vcs, errors.ErrUnsupported)
+	}
+
+	out, err := Run(ctx, r.dir, r.cmd.descendsFrom(rev, tag))
+	if err != nil {
+		return false, err
+	}
+	return strings.TrimSpace(string(out)) != "", nil
 }
 
 func (r *vcsRepo) ReadZip(ctx context.Context, rev, subdir string, maxSize int64) (zip io.ReadCloser, err error) {

src/cmd/go/testdata/script/mod_get_pseudo.txt

@@ -1,82 +1,83 @@
 env GO111MODULE=on
 
-# Testing git->module converter's generation of +incompatible tags; turn off proxy.
-[!net:github.com] skip
 [!git] skip
+[short] skip
+
+# Testing git->module converter's generation of +incompatible tags; turn off proxy.
 env GOPROXY=direct
 env GOSUMDB=off
 
 # We can resolve the @master branch without unshallowing the local repository
 # (even with older gits), so try that before we do anything else.
 # (This replicates https://golang.org/issue/26713 with git 2.7.4.)
-go get github.com/rsc/legacytest@master
+go get vcs-test.golang.org/git/legacytest.git@master
 go list -m all
-stdout '^github.com/rsc/legacytest v2\.0\.1-0\.\d{14}-7303f7796364\+incompatible$'
+stdout '^vcs-test.golang.org/git/legacytest.git v2\.0\.1-0\.\d{14}-7303f7796364\+incompatible$'
 
 # get should include incompatible tags in "latest" calculation.
-go mod edit -droprequire github.com/rsc/legacytest
+go mod edit -droprequire vcs-test.golang.org/git/legacytest.git
-go get github.com/rsc/legacytest@latest
+go get vcs-test.golang.org/git/legacytest.git@latest
 go list
 go list -m all
-stdout '^github.com/rsc/legacytest v2\.0\.0\+incompatible$'
+stdout '^vcs-test.golang.org/git/legacytest.git v2\.0\.0\+incompatible$'
 
 # v2.0.1-0.pseudo+incompatible
-go get ...test@7303f77
+go get ...test.git@7303f77
 go list -m all
-stdout '^github.com/rsc/legacytest v2\.0\.1-0\.\d{14}-7303f7796364\+incompatible$'
+stdout '^vcs-test.golang.org/git/legacytest.git v2\.0\.1-0\.\d{14}-7303f7796364\+incompatible$'
 
 # v2.0.0+incompatible by tag+incompatible
-go get ...test@v2.0.0+incompatible
+go get ...test.git@v2.0.0+incompatible
 go list -m all
-stdout '^github.com/rsc/legacytest v2\.0\.0\+incompatible$'
+stdout '^vcs-test.golang.org/git/legacytest.git v2\.0\.0\+incompatible$'
 
 # v2.0.0+incompatible by tag
-go get ...test@v2.0.0
+go get ...test.git@v2.0.0
 go list -m all
-stdout '^github.com/rsc/legacytest v2\.0\.0\+incompatible$'
+stdout '^vcs-test.golang.org/git/legacytest.git v2\.0\.0\+incompatible$'
 
 # v2.0.0+incompatible by hash (back on master)
-go get ...test@d7ae1e4
+go get ...test.git@d7ae1e4
 go list -m all
-stdout '^github.com/rsc/legacytest v2\.0\.0\+incompatible$'
+stdout '^vcs-test.golang.org/git/legacytest.git v2\.0\.0\+incompatible$'
 
 # v1.2.1-0.pseudo
-go get ...test@d2d4c3e
+go get ...test.git@d2d4c3e
 go list -m all
-stdout '^github.com/rsc/legacytest v1\.2\.1-0\.\d{14}-d2d4c3ea6623$'
+stdout '^vcs-test.golang.org/git/legacytest.git v1\.2\.1-0\.\d{14}-d2d4c3ea6623$'
 
 # v1.2.0
-go get ...test@9f6f860
+go get ...test.git@9f6f860
 go list -m all
-stdout '^github.com/rsc/legacytest v1\.2\.0$'
+stdout '^vcs-test.golang.org/git/legacytest.git v1\.2\.0$'
 
 # v1.1.0-pre.0.pseudo
-go get ...test@fb3c628
+go get ...test.git@fb3c628
 go list -m all
-stdout '^github.com/rsc/legacytest v1\.1\.0-pre\.0\.\d{14}-fb3c628075e3$'
+stdout '^vcs-test.golang.org/git/legacytest.git v1\.1\.0-pre\.0\.\d{14}-fb3c628075e3$'
 
 # v1.1.0-pre (no longer on master)
-go get ...test@731e3b1
+go get ...test.git@731e3b1
 go list -m all
-stdout '^github.com/rsc/legacytest v1\.1\.0-pre$'
+stdout '^vcs-test.golang.org/git/legacytest.git v1\.1\.0-pre$'
 
 # v1.0.1-0.pseudo
-go get ...test@fa4f5d6
+go get ...test.git@fa4f5d6
 go list -m all
-stdout '^github.com/rsc/legacytest v1\.0\.1-0\.\d{14}-fa4f5d6a71c6$'
+stdout '^vcs-test.golang.org/git/legacytest.git v1\.0\.1-0\.\d{14}-fa4f5d6a71c6$'
 
 # v1.0.0
-go get ...test@7fff7f3
+go get ...test.git@7fff7f3
 go list -m all
-stdout '^github.com/rsc/legacytest v1\.0\.0$'
+stdout '^vcs-test.golang.org/git/legacytest.git v1\.0\.0$'
 
 # v0.0.0-pseudo
-go get ...test@52853eb
+go get ...test.git@52853eb
 go list -m all
-stdout '^github.com/rsc/legacytest v0\.0\.0-\d{14}-52853eb7b552$'
+stdout '^vcs-test.golang.org/git/legacytest.git v0\.0\.0-\d{14}-52853eb7b552$'
 
 -- go.mod --
 module x
 -- x.go --
 package x
-import "github.com/rsc/legacytest"
+import "vcs-test.golang.org/git/legacytest.git"

src/cmd/go/testdata/script/mod_get_pseudo_hg.txt

@@ -0,0 +1,81 @@
+env GO111MODULE=on
+
+[!exec:hg] skip
+[short] skip
+
+# Testing hg->module converter's generation of +incompatible tags; turn off proxy.
+env GOPROXY=direct
+env GOSUMDB=off
+
+# get default
+go get vcs-test.golang.org/hg/legacytest.hg@default
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v1\.2\.1-0\.20180717164942-2840708d1294$'
+
+# get should include incompatible tags in "latest" calculation.
+go mod edit -droprequire vcs-test.golang.org/hg/legacytest.hg
+go get vcs-test.golang.org/hg/legacytest.hg@latest
+go list
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v2\.0\.0\+incompatible$'
+
+# v2.0.1-0.pseudo+incompatible
+go get ...test.hg@d6ad6040
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v2\.0\.1-0\.\d{14}-d6ad604046f6\+incompatible$'
+
+# v2.0.0+incompatible by tag+incompatible
+go get ...test.hg@v2.0.0+incompatible
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v2\.0\.0\+incompatible$'
+
+# v2.0.0+incompatible by tag
+go get ...test.hg@v2.0.0
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v2\.0\.0\+incompatible$'
+
+# v2.0.0+incompatible by hash (back on master)
+go get ...test.hg@e64782f
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v2\.0\.0\+incompatible$'
+
+# v1.2.1-0.pseudo
+go get ...test.hg@ed9a22e
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v1\.2\.1-0\.\d{14}-ed9a22ebb8a1$'
+
+# v1.2.0
+go get ...test.hg@07462d
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v1\.2\.0$'
+
+# v1.1.0-pre.0.pseudo
+go get ...test.hg@accb16
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v1\.1\.0-pre\.0\.\d{14}-accb169a3696$'
+
+# v1.1.0-pre (no longer on master)
+go get ...test.hg@90da67a9
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v1\.1\.0-pre$'
+
+# v1.0.1-0.pseudo
+go get ...test.hg@c6260a
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v1\.0\.1-0\.\d{14}-c6260ab8dc3e$'
+
+# v1.0.0
+go get ...test.hg@d6ad17
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v1\.0\.0$'
+
+# v0.0.0-pseudo
+go get ...test.hg@ee0106d
+go list -m all
+stdout '^vcs-test.golang.org/hg/legacytest.hg v0\.0\.0-\d{14}-ee0106da3c7c$'
+
+-- go.mod --
+module x
+-- x.go --
+package x
+import "vcs-test.golang.org/hg/legacytest.hg"

src/cmd/go/testdata/script/reuse_hg.txt

@@ -128,7 +128,7 @@ stdout '"Hash": "1e531550e864b16f25013cfbbf2d8e7cf07a0374"'
 # go mod download vcstest/tagtests@default needs a RepoSum again
 go mod download -x -json vcs-test.golang.org/hg/tagtests.hg@default
 cp stdout tagtestsdefault.json
-stdout '"Version": "v0.0.0-20190509225625-8d0b18b816df"'
+stdout '"Version": "v0.2.3-0.20190509225625-8d0b18b816df"'
 stdout '"Query": "default"'
 stdout '"VCS": "hg"'
 stdout '"URL": ".*/hg/tagtests"'
@@ -292,10 +292,7 @@ go clean -modcache
 go mod download -reuse=tagtestsdefault.json -x -json vcs-test.golang.org/hg/tagtests.hg@default
 ! stderr 'hg( .*)* pull'
 stdout '"Reuse": true'
-  # NOTE: Strictly speaking this should be v0.2.3-... but we never
+stdout '"Version": "v0.2.3-0.20190509225625-8d0b18b816df"'
-  # implemented Mercurial support for finding ancestor tags to
-  # create pseudo-versions.
-stdout '"Version": "v0.0.0-20190509225625-8d0b18b816df"'
 stdout '"Query": "default"'
 stdout '"VCS": "hg"'
 stdout '"URL": ".*/hg/tagtests"'
@@ -310,7 +307,7 @@ go clean -modcache
 go mod download -reuse=all.json -x -json vcs-test.golang.org/hg/tagtests.hg@default
 ! stderr 'hg( .*)* pull'
 stdout '"Reuse": true'
-stdout '"Version": "v0.0.0-20190509225625-8d0b18b816df"'
+stdout '"Version": "v0.2.3-0.20190509225625-8d0b18b816df"'
 stdout '"Query": "default"'
 stdout '"VCS": "hg"'
 stdout '"URL": ".*/hg/tagtests"'

src/cmd/go/testdata/vcstest/git/legacytest.txt

@@ -0,0 +1,118 @@
+handle git
+
+env GIT_AUTHOR_NAME='Russ Cox'
+env GIT_AUTHOR_EMAIL='rsc@golang.org'
+env GIT_COMMITTER_NAME=$GIT_AUTHOR_NAME
+env GIT_COMMITTER_EMAIL=$GIT_AUTHOR_EMAIL
+
+git init
+git branch -M master
+
+at 2018-07-17T12:41:39-04:00
+cp x_cf92c7b.go x.go
+git add x.go
+git commit -m 'initial commit'
+
+at 2018-07-17T12:41:57-04:00
+cp x_52853eb.go x.go
+git commit -m 'add X' x.go
+
+at 2018-07-17T12:42:07-04:00
+cp x_7fff7f3.go x.go
+git commit -m 'gofmt' x.go
+git tag v1.0.0
+
+at 2018-07-17T12:42:28-04:00
+cp x_fa4f5d6.go x.go
+git commit -m 'X->XX' x.go
+
+at 2018-07-17T12:42:36-04:00
+cp x_d7ae1e4.go x.go
+git commit -m 'gofmt' x.go
+git tag v2.0.0
+
+at 2018-07-17T12:42:53-04:00
+cp x_7303f77.go x.go
+git commit -m 'add XXX' x.go
+
+at 2018-07-17T12:47:59-04:00
+git checkout v1.0.0
+cp x_1abc5ff.go x.go
+git commit -m 'comment' x.go
+
+at 2018-07-17T12:48:22-04:00
+cp x_731e3b1.go x.go
+git commit -m 'prerelease' x.go
+git tag v1.1.0-pre
+
+at 2018-07-17T12:48:49-04:00
+cp x_fb3c628.go x.go
+git commit -m 'working' x.go
+
+at 2018-07-17T12:49:05-04:00
+cp x_9f6f860.go x.go
+git commit -m 'v1.2.0' x.go
+git tag v1.2.0
+
+at 2018-07-17T12:49:42-04:00
+cp x_d2d4c3e.go x.go
+git commit -m 'more' x.go
+git tag morework
+
+git show-ref --tags --heads
+cmp stdout .git-refs
+
+-- .git-refs --
+7303f77963648d5f1ec5e55eccfad8e14035866c refs/heads/master
+d2d4c3ea66230e7ad6fbd8f0ecd8c0f851392364 refs/tags/morework
+7fff7f3417faa4a795f9518bc2bef05147a1d6c0 refs/tags/v1.0.0
+731e3b12a0272dcafb560b8fa6a4e9ffb20ef5c9 refs/tags/v1.1.0-pre
+9f6f860fe5c92cd835fdde2913aca8db9ce63373 refs/tags/v1.2.0
+d7ae1e4b368320e7a577fc8a9efc1e78aacac52a refs/tags/v2.0.0
+-- x_1abc5ff.go --
+package legacytest
+
+// add comment
+const X = 1
+-- x_52853eb.go --
+package legacytest
+const X = 1
+-- x_7303f77.go --
+package legacytest
+
+const XX = 2
+
+const XXX = 3
+-- x_731e3b1.go --
+package legacytest
+
+// add comment again
+const X = 1
+-- x_7fff7f3.go --
+package legacytest
+
+const X = 1
+-- x_9f6f860.go --
+package legacytest
+
+// add comment again!!!
+const X = 1
+-- x_cf92c7b.go --
+package legacytest
+-- x_d2d4c3e.go --
+package legacytest
+
+// add comment hack hack hack
+const X = 1
+-- x_d7ae1e4.go --
+package legacytest
+
+const XX = 2
+-- x_fa4f5d6.go --
+package legacytest
+const XX = 2
+-- x_fb3c628.go --
+package legacytest
+
+// add comment fixed
+const X = 1

src/cmd/go/testdata/vcstest/hg/legacytest.txt

@@ -0,0 +1,124 @@
+handle hg
+
+env user='Russ Cox <rsc@golang.org>'
+
+hg init
+
+env date=2018-07-17T12:41:39-04:00
+cp x_cf92c7b.go x.go
+hg add x.go
+hg commit --user=$user --date=$date -m 'initial commit'
+
+env date=2018-07-17T12:41:57-04:00
+cp x_52853eb.go x.go
+hg commit --user=$user --date=$date -m 'add X' x.go
+
+env date=2018-07-17T12:42:07-04:00
+cp x_7fff7f3.go x.go
+hg commit --user=$user --date=$date -m 'gofmt' x.go
+hg tag --user=$user --date=$date v1.0.0
+
+env date=2018-07-17T12:42:28-04:00
+cp x_fa4f5d6.go x.go
+hg commit --user=$user --date=$date -m 'X->XX' x.go
+
+env date=2018-07-17T12:42:36-04:00
+cp x_d7ae1e4.go x.go
+hg commit --user=$user --date=$date -m 'gofmt' x.go
+hg tag --user=$user --date=$date v2.0.0
+
+env date=2018-07-17T12:42:53-04:00
+cp x_7303f77.go x.go
+hg commit --user=$user --date=$date -m 'add XXX' x.go
+
+env date=2018-07-17T12:47:59-04:00
+hg update v1.0.0
+cp x_1abc5ff.go x.go
+hg commit --user=$user --date=$date -m 'comment' x.go
+
+env date=2018-07-17T12:48:22-04:00
+cp x_731e3b1.go x.go
+hg commit --user=$user --date=$date -m 'prerelease' x.go
+hg tag --user=$user --date=$date v1.1.0-pre
+
+env date=2018-07-17T12:48:49-04:00
+cp x_fb3c628.go x.go
+hg commit --user=$user --date=$date -m 'working' x.go
+
+env date=2018-07-17T12:49:05-04:00
+cp x_9f6f860.go x.go
+hg commit --user=$user --date=$date -m 'v1.2.0' x.go
+hg tag --user=$user --date=$date v1.2.0
+
+env date=2018-07-17T12:49:42-04:00
+cp x_d2d4c3e.go x.go
+hg commit --user=$user --date=$date -m 'more' x.go
+hg tag --user=$user --date=$date morework
+
+hg log -r ':' --template '{node|short} {desc|strip|firstline}\n'
+cmp stdout .hg-log
+
+-- .hg-log --
+9dc9138de2e5 initial commit
+ee0106da3c7c add X
+d6ad170f61d4 gofmt
+90c54d4351ee Added tag v1.0.0 for changeset d6ad170f61d4
+c6260ab8dc3e X->XX
+e64782fcadfd gofmt
+d6ad604046f6 Added tag v2.0.0 for changeset e64782fcadfd
+663753d3ac63 add XXX
+4555a6dd66c0 comment
+90da67a9bf0c prerelease
+d7c15fbd635d Added tag v1.1.0-pre for changeset 90da67a9bf0c
+accb169a3696 working
+07462d11385f v1.2.0
+ed9a22ebb8a1 Added tag v1.2.0 for changeset 07462d11385f
+498b291aa133 more
+2840708d1294 Added tag morework for changeset 498b291aa133
+-- x_1abc5ff.go --
+package legacytest
+
+// add comment
+const X = 1
+-- x_52853eb.go --
+package legacytest
+const X = 1
+-- x_7303f77.go --
+package legacytest
+
+const XX = 2
+
+const XXX = 3
+-- x_731e3b1.go --
+package legacytest
+
+// add comment again
+const X = 1
+-- x_7fff7f3.go --
+package legacytest
+
+const X = 1
+-- x_9f6f860.go --
+package legacytest
+
+// add comment again!!!
+const X = 1
+-- x_cf92c7b.go --
+package legacytest
+-- x_d2d4c3e.go --
+package legacytest
+
+// add comment hack hack hack
+const X = 1
+-- x_d7ae1e4.go --
+package legacytest
+
+const XX = 2
+-- x_fa4f5d6.go --
+package legacytest
+const XX = 2
+-- x_fb3c628.go --
+package legacytest
+
+// add comment fixed
+const X = 1