Propagate context and ensure git commands run in request context (#17868)

This PR continues the work in #17125 by progressively ensuring that git
commands run within the request context.

This now means that the if there is a git repo already open in the context it will be used instead of reopening it.

Signed-off-by: Andrew Thornton <art27@cantab.net>

models/db/context.go

@@ -35,7 +35,7 @@ type Context struct {
 func WithEngine(ctx context.Context, e Engine) *Context {
 	return &Context{
 		Context: ctx,
-		e:       e,
+		e:       e.Context(ctx),
 	}
 }
 
@@ -52,6 +52,11 @@ func (ctx *Context) Value(key interface{}) interface{} {
 	return ctx.Context.Value(key)
 }
 
+// WithContext returns this engine tied to this context
+func (ctx *Context) WithContext(other context.Context) *Context {
+	return WithEngine(other, ctx.e)
+}
+
 // Engined structs provide an Engine
 type Engined interface {
 	Engine() Engine

models/db/engine.go

@@ -64,6 +64,7 @@ type Engine interface {
 	Distinct(...string) *xorm.Session
 	Query(...interface{}) ([]map[string][]byte, error)
 	Cols(...string) *xorm.Session
+	Context(ctx context.Context) *xorm.Session
 }
 
 // TableInfo returns table's information via an object