tests: cosmetic improvements to the repo-setup test

Give an overview in "sh t1510-repo-setup.sh --help" output.
Waste some vertical and horizontal space for clearer code.
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t1510-repo-setup.sh

 #!/bin/sh
 
-test_description='Tests of cwd/prefix/worktree/gitdir setup in all cases'
+test_description="Tests of cwd/prefix/worktree/gitdir setup in all cases
 
-. ./test-lib.sh
+A few rules for repo setup:
 
-#
-# 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.
-#
+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-lib.sh
 
-test_repo() {
+test_repo () {
 	(
 		cd "$1" &&
-	if test -n "$2"; then GIT_DIR="$2" && export GIT_DIR; fi &&
-	if test -n "$3"; then GIT_WORK_TREE="$3" && export GIT_WORK_TREE; fi &&
+		if test -n "$2"
+		then
+			GIT_DIR="$2" &&
+			export GIT_DIR
+		fi &&
+		if test -n "$3"
+		then
+			GIT_WORK_TREE="$3" &&
+			export GIT_WORK_TREE
+		fi &&
 		rm -f trace &&
-	GIT_TRACE="`pwd`/trace" git symbolic-ref HEAD >/dev/null &&
+		GIT_TRACE="$(pwd)/trace" git symbolic-ref HEAD >/dev/null &&
 		grep '^setup: ' trace >result &&
 		test_cmp expected result
 	)