CleanPatterns returns the patterns to use for the given command line. It canonicalizes the patterns but does not evaluate any matches.
InDir checks whether path is in the file tree rooted at dir. If so, InDir returns an equivalent path relative to dir. If not, InDir returns an empty string. InDir makes some effort to succeed even in the presence of symbolic links. TODO(rsc): Replace internal/test.inDir with a call to this function for Go 1.12.
IsMetaPackage checks if name is a reserved package name that expands to multiple packages.
IsRelativePath reports whether pattern should be interpreted as a directory path relative to the current directory, as opposed to a pattern matching import paths.
IsStandardImportPath reports whether $GOROOT/src/path should be considered part of the standard distribution. For historical reasons we allow people to add their own code to $GOROOT instead of using $GOPATH, but we assume that code will start with a domain name (dot in the first element).
Note that this function is meant to evaluate whether a directory found in GOROOT should be treated as part of the standard library. It should not be used to decide that a directory found in GOPATH should be rejected: directories in GOPATH need not have dots in the first element, and they just take their chances with future collisions in the standard library.
MatchPattern(pattern)(name) reports whether name matches pattern. Pattern is a limited glob pattern in which '...' means 'any string' and there is no other special syntax. Unfortunately, there are two special cases. Quoting "go help packages":
First, /... at the end of the pattern can match an empty string, so that net/... matches both net and packages in its subdirectories, like net/http. Second, any slash-separted pattern element containing a wildcard never participates in a match of the "vendor" element in the path of a vendored package, so that ./... does not match packages in subdirectories of ./vendor or ./mycode/vendor, but ./vendor/... and ./mycode/vendor/... do. Note, however, that a directory named vendor that itself contains code is not a vendored package: cmd/vendor would be a command named vendor, and the pattern cmd/... matches it.
TreeCanMatchPattern(pattern)(name) reports whether name or children of name can possibly match pattern. Pattern is the same limited glob accepted by matchPattern.
WarnUnmatched warns about patterns that didn't match any packages.
A Match represents the result of matching a single package pattern.
ImportPaths returns the matching paths to use for the given command line. It calls ImportPathsQuiet and then WarnUnmatched.
ImportPathsQuiet is like ImportPaths but does not warn about patterns with no matches.
MatchPackages returns all the packages that can be found under the $GOPATH directories and $GOROOT matching pattern. The pattern is either "all" (all packages), "std" (standard packages), "cmd" (standard commands), or a path including "...".
MatchPackagesInFS is like allPackages but is passed a pattern beginning ./ or ../, meaning it should scan the tree rooted at the given directory. There are ... in the pattern too. (See go help packages for pattern syntax.)