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+---
+title: emacs' git-link and sourcegraph
+date: 2021-08-24
+---
+
+I use [sourcegraph](https://sourcegraph.com/) for searching code, and I sometimes need to share a link to the source code I'm looking at in a buffer. For this, the package [`git-link`](https://github.com/sshaw/git-link) is great.
+
+To integrate sourcegraph and `git-link`, the [documentation](https://github.com/sshaw/git-link#sourcegraph) recommends adding a remote entry named `sourcegraph` in the repository, like this:
+
+```bash
+git remote add sourcegraph https://sourcegraph.com/github.com/sshaw/copy-as-format
+```
+
+The next time you run `M-x git-link` in a buffer, it will use the URL associated with that remote. That's works great, except that now you need to add this for every repository. Instead, for my usage, I came up with the following solution:
+
+    (use-package git-link
+      :ensure t
+      :after magit
+      :bind (("C-c g l" . git-link)
+             ("C-c g a" . git-link-commit))
+      :config
+      (defun fcuny/get-sg-remote-from-hostname (hostname)
+        (format "sourcegraph.<$domain>.<$tld>/%s" hostname))
+
+      (defun fcuny/git-link-work-sourcegraph (hostname dirname filename _branch commit start end)
+        ;;; For a given repository, build the proper link for sourcegraph.
+        ;;; Use the default branch of the repository instead of the
+        ;;; current one (we might be on a feature branch that is not
+        ;;; available on the remote).
+        (require 'magit-branch)
+        (let ((sg-base-url (fcuny/get-sg-remote-from-hostname hostname))
+              (main-branch (magit-main-branch)))
+          (git-link-sourcegraph sg-base-url dirname filename main-branch commit start end)))
+
+      (defun fcuny/git-link-commit-work-sourcegraph (hostname dirname commit)
+        (let ((sg-base-url (fcuny/get-sg-remote-from-hostname hostname)))
+          (git-link-commit-sourcegraph sg-base-url dirname commit)))
+
+      (add-to-list 'git-link-remote-alist '("twitter" fcuny/git-link-work-sourcegraph))
+      (add-to-list 'git-link-commit-remote-alist '("twitter" fcuny/git-link-commit-work-sourcegraph))
+
+      (setq git-link-open-in-browser 't))
+
+We use different domains to host various git repositories at work (e.g. `git.$work`, `gitfoo.$work`, etc). Each of them map to a different URI for sourcegraph (e.g. `sourcegraph.$work/gitfoo`).
+
+`git-link-commit-remote-alist` is an [association list](https://www.gnu.org/software/emacs/manual/html_node/elisp/Association-Lists.html) that takes a regular expression and a function. The custom function receives the hostname for the remote repository, which is then used to generate the URI for our sourcegraph instance. I then call `git-link-sourcegraph` replacing the hostname with the URI for sourcegraph.
+
+Now I can run `M-x git-link` in any repository where the host for the origin git repository matches `twitter` without having to setup the custom remote first.