Add t1510 and basic rules that run repo setup

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1510-repo-setup.sh

@@ -0,0 +1,59 @@
+#!/bin/sh
+
+test_description='Tests of cwd/prefix/worktree/gitdir setup in all cases'
+
+. ./test-lib.sh
+
+#
+# A few rules for repo setup:
+#
+# 1. GIT_DIR is relative to user's cwd. --git-dir is equivalent to
+#    GIT_DIR.
+#
+# 2. .git file is relative to parent directory. .git file is basically
+#    symlink in disguise. The directory where .git file points to will
+#    become new git_dir.
+#
+# 3. core.worktree is relative to git_dir.
+#
+# 4. GIT_WORK_TREE is relative to user's cwd. --work-tree is
+#    equivalent to GIT_WORK_TREE.
+#
+# 5. GIT_WORK_TREE/core.worktree is only effective if GIT_DIR is set
+#    Uneffective worktree settings should be warned.
+#
+# 6. Effective GIT_WORK_TREE overrides core.worktree and core.bare
+#
+# 7. Effective core.worktree conflicts with core.bare
+#
+# 8. If GIT_DIR is set but neither worktree nor bare setting is given,
+#    original cwd becomes worktree.
+#
+# 9. If .git discovery is done inside a repo, the repo becomes a bare
+#    repo. .git discovery is performed if GIT_DIR is not set.
+#
+# 10. If no worktree is available, cwd remains unchanged, prefix is
+#     NULL.
+#
+# 11. When user's cwd is outside worktree, cwd remains unchanged,
+#     prefix is NULL.
+#
+
+test_repo() {
+	(
+	if test -n "$1"; then cd "$1"; fi &&
+	if test -f trace; then rm trace; fi &&
+	GIT_TRACE="`pwd`/trace" git symbolic-ref HEAD >/dev/null &&
+	grep '^setup: ' trace >result &&
+	test_cmp expected result
+	)
+}
+
+# Bit 0 = GIT_WORK_TREE
+# Bit 1 = GIT_DIR
+# Bit 2 = core.worktree
+# Bit 3 = .git is a file
+# Bit 4 = bare repo
+# Case# = encoding of the above 5 bits
+
+test_done