message: vendor: add --explicit-version to docs
diff: @@ -57,6 +57,14 @@ Don\(cqt delete the "vendor" directory when vendoring, but rather keep all
  existing contents of the vendor directory
  .RE
  .sp
  +\fB\-\-explicit\-version\fP
  +.RS 4
  +Normally versions are only added to disambiguate multiple versions of the same package.
  +This option causes all directories in the "vendor" directory to be explicitly versioned,
  +which makes it easier to track the history of vendored packages over time, and can help
  +with the performance of re-vendoring when only a subset of the packages have changed.
  +.RE
  +.sp
  \fB\-\-respect\-source\-config\fP
  .RS 4
  Instead of ignoring \fB[source]\fP configuration by default in \fB.cargo/config\fP
  