checkout: rewrite path specs on command line

When a user gives a path spec to git lfs checkout on the command line,
we turn it into a pattern and then check out only the files specified.
However, currently the user can specify a directory and things will
work, but in the future, we won't automatically rewrite paths for our
file path filter instances.

To handle this gracefully, let's rewrite paths that refer to a literal
directory as paths referring to every path underneath them.  This lets
users write "." and get everything in the current directory, which is
probably what they wanted.

commands/command_checkout.go

@@ -145,10 +145,10 @@ func whichCheckout() (stage git.IndexStage, err error) {
 }
 
 // Parameters are filters
-// firstly convert any pathspecs to the root of the repo, in case this is being
-// executed in a sub-folder
+// firstly convert any pathspecs to patterns relative to the root of the repo,
+// in case this is being executed in a sub-folder
 func rootedPaths(args []string) []string {
-	pathConverter, err := lfs.NewCurrentToRepoPathConverter(cfg)
+	pathConverter, err := lfs.NewCurrentToRepoPatternConverter(cfg)
 	if err != nil {
 		Panic(err, "Could not checkout")
 	}

lfs/util.go

@@ -171,6 +171,41 @@ func (p *currentToRepoPathConverter) Convert(filename string) string {
 	return filepath.ToSlash(reltoroot)
 }
 
+// Convert filenames expressed relative to the current directory to be relative
+// to the repo root and convert them into wildmatch patterns.
+func NewCurrentToRepoPatternConverter(cfg *config.Configuration) (PathConverter, error) {
+	r, c, p, err := pathConverterArgs(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	return &currentToRepoPatternConverter{
+		c: &currentToRepoPathConverter{
+			repoDir:     r,
+			currDir:     c,
+			passthrough: p,
+		},
+	}, nil
+}
+
+type currentToRepoPatternConverter struct {
+	c *currentToRepoPathConverter
+}
+
+func (p *currentToRepoPatternConverter) Convert(filename string) string {
+	pattern := p.c.Convert(filename)
+	if st, err := os.Stat(filename); err == nil && st.IsDir() {
+		pattern += "/"
+	}
+	if strings.HasPrefix(pattern, "./") {
+		pattern = pattern[2:]
+		if len(pattern) == 0 {
+			pattern = "**"
+		}
+	}
+	return pattern
+}
+
 func pathConverterArgs(cfg *config.Configuration) (string, string, bool, error) {
 	currDir, err := os.Getwd()
 	if err != nil {