Follow 307 redirects in simpleApi, even for POST

HTTP client used to automatically follow GET redirects, or turn certain
POST redirects to GET when applicable, but for opening a new pull
request for a renamed repo, we need to repeat the POST against the
updated location.

features/pull_request.feature

@@ -659,3 +659,37 @@ Feature: hub pull-request
       """
     When I successfully run `hub pull-request -m hereyougo`
     Then the output should contain exactly "the://url\n"
+
+  Scenario: Pull request with redirect
+    Given the "origin" remote has url "https://github.com/mislav/coral.git"
+    And I am on the "feature" branch pushed to "origin/feature"
+    Given the GitHub API server:
+      """
+      post('/repos/mislav/coral/pulls') {
+        redirect 'https://api.github.com/repositories/12345', 307
+      }
+      post('/repositories/12345', :host_name => 'api.github.com') {
+        assert :base  => 'master',
+               :head  => 'mislav:feature',
+               :title => 'hereyougo'
+        json :html_url => "the://url"
+      }
+      """
+    When I successfully run `hub pull-request -m hereyougo`
+    Then the output should contain exactly "the://url\n"
+
+  Scenario: Redirect to another host is not followed
+    Given the "origin" remote has url "https://github.com/mislav/coral.git"
+    And I am on the "feature" branch pushed to "origin/feature"
+    Given the GitHub API server:
+      """
+      post('/repos/mislav/coral/pulls') {
+        redirect 'https://disney.com/mouse', 307
+      }
+      """
+    When I run `hub pull-request -m hereyougo`
+    Then the stderr should contain exactly:
+      """
+      Error creating pull request: Temporary Redirect (HTTP 307)
+      Refused to follow redirect to https://disney.com/mouse\n
+      """

github/client.go

@@ -714,6 +714,11 @@ func FormatError(action string, err error) (ee error) {
 			}
 		}
 
+		redirectLocation := e.Response.Header.Get("Location")
+		if statusCode >= 300 && statusCode < 400 && redirectLocation != "" {
+			errorSentences = append(errorSentences, fmt.Sprintf("Refused to follow redirect to %s", redirectLocation))
+		}
+
 		var errorMessage string
 		if len(errorSentences) > 0 {
 			errorMessage = strings.Join(errorSentences, "\n")

github/http.go

@@ -206,13 +206,17 @@ type simpleClient struct {
 	accessToken string
 }
 
-func (c *simpleClient) performRequest(method, path string, body io.Reader, configure func(*http.Request)) (res *simpleResponse, err error) {
+func (c *simpleClient) performRequest(method, path string, body io.Reader, configure func(*http.Request)) (*simpleResponse, error) {
 	url, err := url.Parse(path)
-	if err != nil {
-		return
+	if err == nil {
+		url = c.rootUrl.ResolveReference(url)
+		return c.performRequestUrl(method, url, body, configure, 2)
+	} else {
+		return nil, err
 	}
+}
 
-	url = c.rootUrl.ResolveReference(url)
+func (c *simpleClient) performRequestUrl(method string, url *url.URL, body io.Reader, configure func(*http.Request), redirectsRemaining int) (res *simpleResponse, err error) {
 	req, err := http.NewRequest(method, url.String(), body)
 	if err != nil {
 		return
@@ -223,9 +227,24 @@ func (c *simpleClient) performRequest(method, path string, body io.Reader, confi
 		configure(req)
 	}
 
+	var bodyBackup io.ReadWriter
+	if req.Body != nil {
+		bodyBackup = &bytes.Buffer{}
+		req.Body = ioutil.NopCloser(io.TeeReader(req.Body, bodyBackup))
+	}
+
 	httpResponse, err := c.httpClient.Do(req)
-	if err == nil {
-		res = &simpleResponse{httpResponse}
+	if err != nil {
+		return
+	}
+
+	res = &simpleResponse{httpResponse}
+	if res.StatusCode == 307 && redirectsRemaining > 0 {
+		url, err = url.Parse(res.Header.Get("Location"))
+		if err != nil || url.Host != req.URL.Host || url.Scheme != req.URL.Scheme {
+			return
+		}
+		res, err = c.performRequestUrl(method, url, bodyBackup, configure, redirectsRemaining-1)
 	}
 
 	return