[LibGit2] Teach tests to be resilient to init.defaultBranch (#44629)

If a user runs the tests with a `~/.gitconfig` that provides an
`init.defaultBranch` that is not `master`, our tests fail.  Let's adjust
to the user's configuration as appropriate.  We'll also rename this to
`default_branch` to signify that it may not be called `master` anymore.

(cherry picked from commit ac1d693)

stdlib/LibGit2/test/libgit2.jl

@@ -634,7 +634,7 @@ mktempdir() do dir
  commit_oid1 = LibGit2.GitHash()
  commit_oid2 = LibGit2.GitHash()
  commit_oid3 = LibGit2.GitHash()
- master_branch = "master"
+ default_branch = LibGit2.getconfig("init.defaultBranch", "master")
  test_branch = "test_branch"
  test_branch2 = "test_branch_two"
  tag1 = "tag1"
@@ -958,19 +958,19 @@ mktempdir() do dir
  # various branch properties
  @test LibGit2.isbranch(brref)
  @test !LibGit2.isremote(brref)
- @test LibGit2.name(brref) == "refs/heads/master"
- @test LibGit2.shortname(brref) == master_branch
+ @test LibGit2.name(brref) == "refs/heads/$(default_branch)"
+ @test LibGit2.shortname(brref) == default_branch
  @test LibGit2.ishead(brref)
  @test LibGit2.upstream(brref) === nothing
 
  # showing the GitReference to this branch
  show_strs = split(sprint(show, brref), "\n")
  @test show_strs[1] == "GitReference:"
- @test show_strs[2] == "Branch with name refs/heads/master"
+ @test show_strs[2] == "Branch with name refs/heads/$(default_branch)"
  @test show_strs[3] == "Branch is HEAD."
  @test repo.ptr == LibGit2.repository(brref).ptr
- @test brnch == master_branch
- @test LibGit2.headname(repo) == master_branch
+ @test brnch == default_branch
+ @test LibGit2.headname(repo) == default_branch
 
  # create a branch *without* setting its tip as HEAD
  LibGit2.branch!(repo, test_branch, string(commit_oid1), set_head=false)
@@ -991,7 +991,7 @@ mktempdir() do dir
  end
  end
  branches = map(b->LibGit2.shortname(b[1]), LibGit2.GitBranchIter(repo))
- @test master_branch in branches
+ @test default_branch in branches
  @test test_branch in branches
  end
  end
@@ -1050,7 +1050,7 @@ mktempdir() do dir
  @test tag2 in tags
 
  refs = LibGit2.ref_list(repo)
- @test refs == ["refs/heads/master", "refs/heads/test_branch", "refs/tags/tag1", "refs/tags/tag2"]
+ @test refs == ["refs/heads/$(default_branch)", "refs/heads/test_branch", "refs/tags/tag1", "refs/tags/tag2"]
  # test deleting a tag
  LibGit2.tag_delete(repo, tag1)
  tags = LibGit2.tag_list(repo)
@@ -1334,7 +1334,7 @@ mktempdir() do dir
  add_and_commit_file(repo, "file1", "111\n")
  # switch back, add a commit, try to merge
  # from branch/merge_a
- LibGit2.branch!(repo, "master")
+ LibGit2.branch!(repo, default_branch)
 
  # test for showing a Reference to a non-HEAD branch
  brref = LibGit2.GitReference(repo, "refs/heads/branch/merge_a")
@@ -1347,7 +1347,7 @@ mktempdir() do dir
 
  add_and_commit_file(repo, "file2", "222\n")
  upst_ann = LibGit2.GitAnnotated(repo, "branch/merge_a")
- head_ann = LibGit2.GitAnnotated(repo, "master")
+ head_ann = LibGit2.GitAnnotated(repo, default_branch)
 
  # (fail to) merge them because we can't fastforward
  @test_logs (:warn,"Cannot perform fast-forward merge") !LibGit2.merge!(repo, [upst_ann], true)
@@ -1360,7 +1360,7 @@ mktempdir() do dir
  mv(joinpath(LibGit2.path(repo),"file1"),joinpath(LibGit2.path(repo),"mvfile1"))
  LibGit2.add!(repo, "mvfile1")
  LibGit2.commit(repo, "move file1")
- LibGit2.branch!(repo, "master")
+ LibGit2.branch!(repo, default_branch)
  upst_ann = LibGit2.GitAnnotated(repo, "branch/merge_b")
  rename_flag = Cint(0)
  rename_flag = LibGit2.toggle(rename_flag, Cint(0)) # turns on the find renames opt
@@ -1438,14 +1438,14 @@ mktempdir() do dir
  # the rebase should fail.
  @test_throws LibGit2.GitError LibGit2.rebase!(repo)
  # Try rebasing on master instead
- newhead = LibGit2.rebase!(repo, master_branch)
+ newhead = LibGit2.rebase!(repo, default_branch)
  @test newhead == head_oid
 
  # Switch to the master branch
- LibGit2.branch!(repo, master_branch)
+ LibGit2.branch!(repo, default_branch)
 
  fetch_heads = LibGit2.fetchheads(repo)
- @test fetch_heads[1].name == "refs/heads/master"
+ @test fetch_heads[1].name == "refs/heads/$(default_branch)"
  @test fetch_heads[1].ismerge == true # we just merged master
  @test fetch_heads[2].name == "refs/heads/test_branch"
  @test fetch_heads[2].ismerge == false
@@ -1485,7 +1485,7 @@ mktempdir() do dir
 
  # all tag in place
  branches = map(b->LibGit2.shortname(b[1]), LibGit2.GitBranchIter(repo))
- @test master_branch in branches
+ @test default_branch in branches
  @test test_branch in branches
 
  # issue #16337
@@ -1683,7 +1683,7 @@ mktempdir() do dir
  # add yet another file
  add_and_commit_file(repo, "file4", "444\n")
  # rebase with onto
- newhead = LibGit2.rebase!(repo, "branch/a", "master")
+ newhead = LibGit2.rebase!(repo, "branch/a", default_branch)
 
  newerhead = LibGit2.head_oid(repo)
  @test newerhead == newhead
@@ -1693,7 +1693,7 @@ mktempdir() do dir
  pre_abort_head = add_and_commit_file(repo, "file6", "666\n")
  # Rebase type
  head_ann = LibGit2.GitAnnotated(repo, "branch/a")
- upst_ann = LibGit2.GitAnnotated(repo, "master")
+ upst_ann = LibGit2.GitAnnotated(repo, default_branch)
  rb = LibGit2.GitRebase(repo, head_ann, upst_ann)
  @test_throws BoundsError rb[3]
  @test_throws BoundsError rb[0]
@@ -1718,7 +1718,7 @@ mktempdir() do dir
 
  a_head = LibGit2.head_oid(repo)
  add_and_commit_file(repo, "merge_file1", "111\n")
- LibGit2.branch!(repo, "master")
+ LibGit2.branch!(repo, default_branch)
  a_head_ann = LibGit2.GitAnnotated(repo, "branch/merge_a")
  # merge returns true if successful
  @test_logs (:info,"Review and commit merged changes") LibGit2.merge!(repo, [a_head_ann])