Improve support for default branches (#231, #232)

Unless a branch is specified, the default remote HEAD is used during
clone. Also a local master branch is not created if it is not the remote
HEAD.

test/test_clone.py

@@ -70,6 +70,9 @@ def test_clone(
         # clone should succeed, and repo should be configured properly
         assert successful_clone(run, paths, repo_config)
 
+        # these clones should have master as HEAD
+        verify_head(paths, 'master')
+
         # ensure conflicts are handled properly
         if conflicts:
             assert 'NOTE' in run.out
@@ -162,6 +165,7 @@ def test_clone_bootstrap(
         assert BOOTSTRAP_MSG not in run.out
 
     assert successful_clone(run, paths, repo_config, expected_code)
+    verify_head(paths, 'master')
 
     if not bs_exists:
         assert BOOTSTRAP_MSG not in run.out
@@ -230,6 +234,7 @@ def test_clone_perms(
     )
 
     assert successful_clone(run, paths, repo_config)
+    verify_head(paths, 'master')
     if in_work:
         # private directories which already exist, should be left as they are,
         # which in this test is "insecure".
@@ -260,7 +265,8 @@ def test_clone_perms(
 
 
 @pytest.mark.usefixtures('remote')
-@pytest.mark.parametrize('branch', ['master', 'valid', 'invalid'])
+@pytest.mark.parametrize(
+    'branch', ['master', 'default', 'valid', 'invalid'])
 def test_alternate_branch(runner, paths, yadm_cmd, repo_config, branch):
     """Test cloning a branch other than master"""
 
@@ -269,6 +275,12 @@ def test_alternate_branch(runner, paths, yadm_cmd, repo_config, branch):
     os.system(
         f'GIT_DIR="{paths.remote}" git commit '
         f'--allow-empty -m "This branch is valid"')
+    if branch != 'default':
+        # When branch == 'default', the "default" branch of the remote repo
+        # will remain "valid" to validate identification the correct default
+        # branch by inspecting the repo. Otherwise it will be set back to
+        # "master"
+        os.system(f'GIT_DIR="{paths.remote}" git checkout master')
 
     # clear out the work path
     paths.work.remove()
@@ -278,7 +290,7 @@ def test_alternate_branch(runner, paths, yadm_cmd, repo_config, branch):
 
     # run the clone command
     args = ['clone', '-w', paths.work]
-    if branch != 'master':
+    if branch not in ['master', 'default']:
         args += ['-b', branch]
     args += [remote_url]
     run = runner(command=yadm_cmd(*args))
@@ -298,10 +310,12 @@ def test_alternate_branch(runner, paths, yadm_cmd, repo_config, branch):
         assert run.err == ''
         assert f'origin\t{remote_url}' in run.out
         run = runner(command=yadm_cmd('show'))
-        if branch == 'valid':
+        if branch == 'master':
-            assert 'This branch is valid' in run.out
-        else:
             assert 'Initial commit' in run.out
+            verify_head(paths, 'master')
+        else:
+            assert 'This branch is valid' in run.out
+            verify_head(paths, 'valid')
 
 
 def successful_clone(run, paths, repo_config, expected_code=0):
@@ -324,3 +338,16 @@ def remote(paths, ds1_repo_copy):
     # cannot be applied to another fixture.
     paths.remote.remove()
     paths.repo.move(paths.remote)
+
+
+def test_no_repo(runner, yadm_cmd, ):
+    """Test cloning without specifying a repo"""
+    run = runner(command=yadm_cmd('clone'))
+    assert run.failure
+    assert run.err == ''
+    assert 'ERROR: No repository provided' in run.out
+
+
+def verify_head(paths, branch):
+    """Assert the local repo has the correct head branch"""
+    assert paths.repo.join('HEAD').read() == f'ref: refs/heads/{branch}\n'

test/test_default_remote_branch.py

@@ -0,0 +1,27 @@
+"""Unit tests: _default_remote_branch()"""
+import pytest
+
+
+@pytest.mark.parametrize('condition', ['found', 'missing'])
+def test(runner, paths, condition):
+    """Test _default_remote_branch()"""
+    test_branch = 'test/branch'
+    output = f'ref: refs/heads/{test_branch}\\tHEAD\\n'
+    if condition == 'missing':
+        output = 'output that is missing ref'
+    script = f"""
+        YADM_TEST=1 source {paths.pgm}
+        function git() {{
+          printf '{output}';
+          printf 'mock stderr\\n' 1>&2
+        }}
+        _default_remote_branch URL
+    """
+    print(condition)
+    run = runner(command=['bash'], inp=script)
+    assert run.success
+    assert run.err == ''
+    if condition == 'found':
+        assert run.out.strip() == test_branch
+    else:
+        assert run.out.strip() == 'master'

yadm

@@ -743,13 +743,23 @@ function clean() {
 
 }
 
+function _default_remote_branch() {
+  local ls_remote
+  ls_remote=$("$GIT_PROGRAM" ls-remote -q --symref "$1" 2>/dev/null)
+  match="^ref:[[:blank:]]+refs/heads/([^[:blank:]]+)"
+  if [[ "$ls_remote" =~ $match ]] ; then
+    echo "${BASH_REMATCH[1]}"
+  else
+    echo master
+  fi
+}
+
 function clone() {
 
   DO_BOOTSTRAP=1
-  local branch
+  local branch=
-  branch="master"
 
-  clone_args=()
+  local repo_url=
   while [[ $# -gt 0 ]] ; do
     key="$1"
     case $key in
@@ -766,22 +776,29 @@ function clone() {
       --no-bootstrap) # prevent bootstrap, without prompt
         DO_BOOTSTRAP=3
       ;;
-      *) # main arguments are kept intact
+      *) # use first found argument as the URL
-        clone_args+=("$1")
+        [ -z "$repo_url" ] && repo_url="$1"
       ;;
     esac
     shift
   done
 
+  [ -z "$repo_url" ] && error_out "No repository provided"
+
+  [ -z "$branch" ] && branch=$(_default_remote_branch "$repo_url")
+
   [ -n "$DEBUG" ] && display_private_perms "initial"
 
+  # shellcheck disable=SC2119
   # clone will begin with a bare repo
-  local empty=
+  init
-  init $empty
+
+  # configure local HEAD with the correct branch
+  printf 'ref: refs/heads/%s\n' "$branch" > "${YADM_REPO}/HEAD"
 
   # add the specified remote, and configure the repo to track origin/$branch
   debug "Adding remote to new repo"
-  "$GIT_PROGRAM" remote add origin "${clone_args[@]}"
+  "$GIT_PROGRAM" remote add origin "$repo_url"
   debug "Configuring new repo to track origin/${branch}"
   "$GIT_PROGRAM" config "branch.${branch}.remote" origin
   "$GIT_PROGRAM" config "branch.${branch}.merge" "refs/heads/${branch}"
@@ -791,13 +808,13 @@ function clone() {
   "$GIT_PROGRAM" fetch origin || {
     debug "Removing repo after failed clone"
     rm -rf "$YADM_REPO"
-    error_out "Unable to fetch origin ${clone_args[0]}"
+    error_out "Unable to fetch origin $repo_url"
   }
   debug "Verifying '${branch}' is a valid branch to merge"
   [ -f "${YADM_REPO}/refs/remotes/origin/${branch}" ] || {
     debug "Removing repo after failed clone"
     rm -rf "$YADM_REPO"
-    error_out "Clone failed, 'origin/${branch}' does not exist in ${clone_args[0]}"
+    error_out "Clone failed, 'origin/${branch}' does not exist in $repo_url"
   }
 
   if [ "$YADM_WORK" = "$HOME" ]; then
@@ -1164,6 +1181,7 @@ EOF
 
 }
 
+# shellcheck disable=SC2120
 function init() {
 
   # safety check, don't attempt to init when the repo is already present

yadm.1

@@ -116,12 +116,10 @@ if it exists.
 .BI clone " url
 Clone a remote repository for tracking dotfiles.
 After the contents of the remote repository have been fetched, a "merge" of
-.I origin/master
+the remote HEAD branch is attempted.
-is attempted.
 If there are conflicting files already present in the
 .IR work-tree ,
-this merge will fail and instead a "reset" of
+this merge will fail and instead a "reset" of the remote HEAD branch
-.I origin/master
 will be done, followed by a "stash". This "stash" operation will preserve the
 original data.
 
@@ -154,8 +152,7 @@ but this can be overridden with the
 .BR -w " option.
 yadm can be forced to overwrite an existing repository by providing the
 .BR -f " option.
-If you want to use a branch other than
+If you want to use a branch other than the remote HEAD branch
-.IR origin/master ,
 you can specify it using the
 .BR -b " option.
 By default yadm will ask the user if the bootstrap program should be run (if it