… mod tidy' of modules before 'go 1.21'

This eliminate a network access in 'go mod tidy' of an already-tidy
module, which would otherwise be needed to fetch go.mod checksums for
the test dependencies whose go.mod checksums were omitted in Go
releases between Go 1.17 and 1.20 due to bug #56222.

For modules between 'go 1.17' and 'go 1.20' we intentionally preserve
the old 'go mod tidy' output (omitting go.sum entries for the go.mod
files of test dependencies of external packages). We should also avoid
performing extra sumdb lookups for checksums that would be discarded
anyway.

Updates #56222.

Change-Id: I7f0f1c8e902db0e3414c819621c4b99052f503f0
Reviewed-on: https://go-review.googlesource.com/c/go/+/492741
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

…d for go version lines

When we load a package from a module, we need the go version line from
that module's go.mod file to know what language semantics to use for
the package. We need to save a checksum for the go.mod file even if
the module's requirements are pruned out of the module graph.
Previously, we were missing checksums for test dependencies of
packages in 'all' and packages passed to 'go get -t'.

This change preserves the existing bug for 'go mod tidy',
but fixes it for 'go get -t' and flags the missing checksum
with a clearer error in other cases.

Fixes #60001.
Updates #56222.

Change-Id: Icd6acce348907621ae0b02dbeac04fb180353dcf
(cherry picked from CL 489075 and CL 492741)
Reviewed-on: https://go-review.googlesource.com/c/go/+/493015
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>

…d for go version lines

When we load a package from a module, we need the go version line from
that module's go.mod file to know what language semantics to use for
the package. We need to save a checksum for the go.mod file even if
the module's requirements are pruned out of the module graph.
Previously, we were missing checksums for test dependencies of
packages in 'all' and packages passed to 'go get -t'.

This change preserves the existing bug for 'go mod tidy',
but fixes it for 'go get -t' and flags the missing checksum
with a clearer error in other cases.

Fixes #60000.
Updates #56222.

Change-Id: Icd6acce348907621ae0b02dbeac04fb180353dcf
(cherry picked from CL 489075 and CL 492741)
Reviewed-on: https://go-review.googlesource.com/c/go/+/492983
Reviewed-by: Michael Matloob <matloob@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Bypass: Bryan Mills <bcmills@google.com>

…ore often in pre-1.21 modules

This updates the logic from CL 489075 to avoid trying to save extra
sums if they aren't already expected to be present
and cfg.BuildMod != "mod" (as in the case of "go list -m -u all" with
a go.mod file that specifies go < 1.21).

Fixes #60667.
Updates #56222.

Change-Id: Ied6ed3e80a62f9cd9a328b43a415a42d14481056
Reviewed-on: https://go-review.googlesource.com/c/go/+/502015
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

…d for go version lines more often in pre-1.21 modules

This updates the logic from CL 489075 to avoid trying to save extra
sums if they aren't already expected to be present
and cfg.BuildMod != "mod" (as in the case of "go list -m -u all" with
a go.mod file that specifies go < 1.21).

Fixes #60698.
Updates #60667.
Updates #56222.

Change-Id: Ied6ed3e80a62f9cd9a328b43a415a42d14481056
Reviewed-on: https://go-review.googlesource.com/c/go/+/502016
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>

…d for go version lines more often in pre-1.21 modules

This updates the logic from CL 489075 to avoid trying to save extra
sums if they aren't already expected to be present
and cfg.BuildMod != "mod" (as in the case of "go list -m -u all" with
a go.mod file that specifies go < 1.21).

Fixes #60697.
Updates #60667.
Updates #56222.

Change-Id: Ied6ed3e80a62f9cd9a328b43a415a42d14481056
Reviewed-on: https://go-review.googlesource.com/c/go/+/502017
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Bypass: Bryan Mills <bcmills@google.com>