Expand variables in redir includes

Expand variables in <$file style includes. Fixes
dcjones#9.

go.mod

@@ -5,4 +5,5 @@ go 1.14
 require (
 	github.com/google/go-cmp v0.4.0
 	github.com/mattn/go-isatty v0.0.12
+	github.com/sanity-io/litter v1.2.0
 )

go.sum

@@ -1,7 +1,12 @@
+github.com/davecgh/go-spew v0.0.0-20161028175848-04cdfd42973b/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
+github.com/pmezard/go-difflib v0.0.0-20151028094244-d8ed2627bdf0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sanity-io/litter v1.2.0 h1:DGJO0bxH/+C2EukzOSBmAlxmkhVMGqzvcx/rvySYw9M=
+github.com/sanity-io/litter v1.2.0/go.mod h1:JF6pZUFgu2Q0sBZ+HSV35P8TVPI1TTzEwyu9FXAw2W4=
+github.com/stretchr/testify v0.0.0-20161117074351-18a02ba4a312/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42 h1:vEOn+mP2zCOVzKckCZy6YsCtDblrpj/w7B9nxGNELpg=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

mk_test.go

@@ -67,7 +67,7 @@ func TestBasicMaking(t *testing.T) {
 			input:  "testdata/test7.mk",
 			output: "testdata/test7.mk.expected",
 			errors: "",
-			passes: false,
+			passes: true,
 		},
 		{
 			// Variables expanded in recipes.

parse.go

@@ -117,7 +117,7 @@ func parsePipeInclude(p *parser, t token) parserStateFun {
 		for i := 0; i < len(p.tokenbuf); i++ {
 			args[i] = p.tokenbuf[i].val
 		}
-		
+
 		// TODO - might have $shell available by now, but maybe not?
 		// It's not populated, regardless
 		var shell string
@@ -164,9 +164,16 @@ func parseRedirInclude(p *parser, t token) parserStateFun {
 		for i := range p.tokenbuf {
 			filename += p.tokenbuf[i].val
 		}
-
-		filename = os.ExpandEnv(filename)
-
+
+		// Expand variables in paths.
+		parts := expand(filename, p.rules.vars, false)
+		if len(parts) != 1 {
+			mkError("filename variables need to be a single value")
+		}
+
+		// TODO(rjk): Be sure that this is the right behaviour.
+		filename = parts[0]
+
 		file, err := os.Open(filename)
 		if err != nil {
 			p.basicErrorAtToken(fmt.Sprintf("cannot open %s", filename), p.tokenbuf[0])
@@ -315,7 +322,7 @@ func parseRecipe(p *parser, t token) parserStateFun {
 			msg := fmt.Sprintf("while reading a rule's attributes expected an attribute but found \"%c\".", err.found)
 			p.basicErrorAtToken(msg, p.tokenbuf[i+1])
 		}
-		
+
 		// If we don't have a shell set, check vars, check default shell
 		if r.shell == nil {
 			if len(p.rules.vars["shell"]) > 0 {