1 files changed, 78 insertions, 0 deletions
diff --git a/remote.go b/remote.go
new file mode 100644
index 0000000..ed5efd7
--- /dev/null
+++ b/remote.go
@@ -0,0 +1,78 @@
+/*******************************************************************************
+*
+* Copyright 2017 Stefan Majewsky <majewsky@gmx.net>
+*
+* This program is free software: you can redistribute it and/or modify it under
+* the terms of the GNU General Public License as published by the Free Software
+* Foundation, either version 3 of the License, or (at your option) any later
+* version.
+*
+* This program is distributed in the hope that it will be useful, but WITHOUT ANY
+* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+* A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License along with
+* this program. If not, see <http://www.gnu.org/licenses/>.
+*
+*******************************************************************************/
+
+package main
+
+import (
+	"bytes"
+	"os/exec"
+	"regexp"
+	"strings"
+)
+
+//remoteAlias describes an alias that can be used in a Git remote URL (as
+//defined by the "url.<base>.insteadOf" directive in man:git-config(1)).
+type remoteAlias struct {
+	Alias       string
+	Replacement string
+}
+
+var remoteAliases []*remoteAlias
+
+func init() {
+	cmd := exec.Command("git", "config", "--global", "-l")
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	FatalIfError(cmd.Run())
+
+	rx := regexp.MustCompile(`^url\.([^=]+)\.insteadof=(.+)$`)
+	for _, line := range strings.Split(string(buf.Bytes()), "\n") {
+		match := rx.FindStringSubmatch(line)
+		if match == nil {
+			continue
+		}
+		remoteAliases = append(remoteAliases, &remoteAlias{
+			Alias:       match[2],
+			Replacement: match[1],
+		})
+	}
+}
+
+//ExpandRemoteURL derive the canonical URL for a given remote by substituting
+//aliases defined in the system-wide and user-global Git config. For example,
+//with
+//
+//    $ cat /etc/gitconfig
+//    [url "git://github.com/"]
+//    insteadOf = gh:
+//
+//and the input "gh:foo/bar", this function returns "git://github.com/foo/bar".
+func ExpandRemoteURL(url string) string {
+	var best *remoteAlias
+	for _, current := range remoteAliases {
+		if strings.HasPrefix(url, current.Alias) {
+			if best == nil || len(best.Alias) < len(current.Alias) {
+				best = current
+			}
+		}
+	}
+	if best == nil {
+		return url
+	}
+	return best.Replacement + strings.TrimPrefix(url, best.Alias)
+}