[jhbuild/ls_remote_main_branch: 1/2] get default branch name from remote repository

[Nelson Ben <nbenitez src gnome org>]

commit 2d12a60461a2625c78559516a9305e843ad5afcb
Author: Nelson Benítez León <nbenitezl gmail com>
Date:   Thu Jan 20 16:01:03 2022 -0400

    get default branch name from remote repository
    
    commit 77192689d retrieves the branch name from
    the local repository, so it worked fine for new
    cloned repositories, but if you have an already
    cloned repository then you'll still be getting
    the old default branch name.
    
    Fix this by using command:
    git ls-remote --symref origin HEAD
    
    which will retrieve the default branch name
    from the remote repository itself.
    
    As a plus 'git ls-remote' is a plumbing command
    in git which means it has stable output well
    suited for scripts.

 jhbuild/versioncontrol/git.py | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)
---
diff --git a/jhbuild/versioncontrol/git.py b/jhbuild/versioncontrol/git.py
index c2d21738..460dbe5b 100644
--- a/jhbuild/versioncontrol/git.py
+++ b/jhbuild/versioncontrol/git.py
@@ -238,13 +238,26 @@ class GitBranch(Branch):
 
     def get_default_branch_name(self):
         try:
-            default_branch = get_output(['git', 'symbolic-ref', '--short',
-                               'refs/remotes/origin/HEAD'],
-                               cwd=self.get_checkoutdir(),
-                               extra_env=get_git_extra_env()).strip()
+            out = get_output(['git', 'ls-remote', '--symref', 'origin', 'HEAD'],
+                    cwd=self.get_checkoutdir(),
+                    extra_env=get_git_extra_env()).strip()
         except CommandError:
-            return 'master'
-        return default_branch.replace('origin/', '')
+            logging.warning('get_default_branch_name() command error, so defaulting to \'main\'')
+            return 'main'
+
+        ind = out.find("ref: ")
+        if ind == -1:
+            logging.warning('Unexpected get_default_branch_name() output, so defaulting to \'main\'')
+            return 'main'
+
+        tmp = out[ind:].split("\t", maxsplit=1)
+        if len(tmp) == 2 and tmp[1][0:4] == "HEAD":
+            default_branch = tmp[0].split("/")[-1]
+        else:
+            logging.warning('Unexpected get_default_branch_name() output, so defaulting to \'main\'')
+            default_branch = 'main'
+
+        return default_branch
 
     def get_branch_switch_destination(self):
         current_branch = self.get_current_branch()