Make runs-on support variable expression (#91)

Partial implementation of https://gitea.com/gitea/act_runner/issues/445, the Gitea side also needs a PR for the entire functionality.
Gitea side: go-gitea/gitea#29468

Co-authored-by: Jason Song <i@wolfogre.com>
Reviewed-on: https://gitea.com/gitea/act/pulls/91
Reviewed-by: Jason Song <i@wolfogre.com>
Co-authored-by: sillyguodong <gedong_1994@163.com>
Co-committed-by: sillyguodong <gedong_1994@163.com>

pkg/jobparser/interpeter.go

@@ -15,6 +15,7 @@ func NewInterpeter(
 	matrix map[string]interface{},
 	gitCtx *model.GithubContext,
 	results map[string]*JobResult,
+	vars map[string]string,
 ) exprparser.Interpreter {
 	strategy := make(map[string]interface{})
 	if job.Strategy != nil {
@@ -62,6 +63,7 @@ func NewInterpeter(
 		Matrix:   matrix,
 		Needs:    using,
 		Inputs:   nil, // not supported yet
+		Vars:     vars,
 	}
 
 	config := exprparser.Config{

pkg/jobparser/jobparser.go

@@ -53,7 +53,7 @@ func Parse(content []byte, options ...ParseOption) ([]*SingleWorkflow, error) {
 			}
 			job.Name = nameWithMatrix(job.Name, matrix)
 			job.Strategy.RawMatrix = encodeMatrix(matrix)
-			evaluator := NewExpressionEvaluator(NewInterpeter(id, origin.GetJob(id), matrix, pc.gitContext, results))
+			evaluator := NewExpressionEvaluator(NewInterpeter(id, origin.GetJob(id), matrix, pc.gitContext, results, pc.vars))
 			runsOn := origin.GetJob(id).RunsOn()
 			for i, v := range runsOn {
 				runsOn[i] = evaluator.Interpolate(v)
@@ -86,9 +86,16 @@ func WithGitContext(context *model.GithubContext) ParseOption {
 	}
 }
 
+func WithVars(vars map[string]string) ParseOption {
+	return func(c *parseContext) {
+		c.vars = vars
+	}
+}
+
 type parseContext struct {
 	jobResults map[string]string
 	gitContext *model.GithubContext
+	vars       map[string]string
 }
 
 type ParseOption func(c *parseContext)