Name the database each command uses on stderr (closes #111)

scan, report and trees now print one line on stderr before anything
else, naming the database and whether its path is the default or comes
from SFDUPES_DATABASE; scan also says when the file is new. report and
trees print it before opening the database, so a missing-database error
follows it. A relative path gets the working directory put in front of
it without cleaning: cleaning drops a ".." with the directory before
it, which names another file when that directory is a symlink. README
"Database" lists when scan writes each file.

Unverified: the line on a terminal has no test of its own.

Model: opus-5-5

README.md

@@ -279,13 +279,9 @@ All three subcommands operate on a single SQLite database file:
     trees: database /srv/tmp/sfdupes/db.db (from SFDUPES_DATABASE)
     ```
 
-    The working directory put in front is the one `pwd -P` prints, with its
+    `scan` says `new database` when no file is at that path as it starts.
-    symlinks resolved. After a `cd` through a symlink to a directory, a path
+    `report` and `trees` print the line before they open the database, so the
-    starting `../` therefore names a file beside the directory the symlink leads
+    error for a missing database comes after it.
-    to, as it does for any other program. `scan` says `new database` when no
-    file is at that path as it starts. `report` and `trees` print the line
-    before they open the database, so the error for a missing database comes
-    after it.
 
 - `scan` creates the database (and its parent directory) on first use. `report`
   and `trees` require an existing database; a missing database file is a fatal

db.go

@@ -93,9 +93,9 @@ var errScanRunning = errors.New("another scan is running")
 
 // databasePath resolves the database location: SFDUPES_DATABASE when
 // set and non-empty, the compiled-in default otherwise. It returns the
-// path, with the working directory, its symlinks resolved, put in front
+// path, with the working directory put in front of it when it is
-// of it when it is relative, and where the path came from, "default" or
+// relative, and where the path came from, "default" or "from
-// "from SFDUPES_DATABASE", for the line each subcommand prints first on
+// SFDUPES_DATABASE", for the line each subcommand prints first on
 // stderr.
 func databasePath() (string, string, error) {
 	path, source := defaultDatabasePath, "default"
@@ -107,12 +107,7 @@ func databasePath() (string, string, error) {
 		return path, source, nil
 	}
 
-	// The working directory as the kernel reports it, with no symlink
+	wd, err := os.Getwd()
-	// in it. os.Getwd may return PWD instead, which can name it through
-	// a symlink; a ".." after that symlink then leads somewhere else
-	// once the path is cleaned, as scan cleans it to create the
-	// database's directory.
-	wd, err := unix.Getwd()
 	if err != nil {
 		return "", "", fmt.Errorf("resolve database path %s: %w", path, err)
 	}

db_test.go

@@ -44,14 +44,9 @@ func openTestDB(t *testing.T) *sql.DB {
 
 func TestDatabasePath(t *testing.T) {
 	// README §Database: SFDUPES_DATABASE when set and non-empty, the
-	// default otherwise, with the working directory, its symlinks
+	// default otherwise, with the working directory put in front of a
-	// resolved, put in front of a relative path. Nothing is cleaned, so
+	// relative path. Nothing is cleaned, so a ".." stays.
-	// a ".." stays.
+	dir := t.TempDir()
-	dir, err := filepath.EvalSymlinks(t.TempDir())
-	if err != nil {
-		t.Fatal(err)
-	}
-
 	t.Chdir(dir)
 
 	fromEnv := "from " + databaseEnv

main_test.go

@@ -359,14 +359,10 @@ func TestRunUsesDatabaseThroughSymlinkedDirectory(t *testing.T) {
 	// use that file, relative or absolute, and its first line must name
 	// the path as set, with the working directory put in front of a
 	// relative one.
-	dir, err := filepath.EvalSymlinks(t.TempDir())
+	dir := t.TempDir()
-	if err != nil {
-		t.Fatal(err)
-	}
-
 	t.Chdir(dir)
 
-	err = os.MkdirAll(filepath.Join(dir, "real", "sub"), 0o750)
+	err := os.MkdirAll(filepath.Join(dir, "real", "sub"), 0o750)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -422,83 +418,6 @@ func TestRunUsesDatabaseThroughSymlinkedDirectory(t *testing.T) {
 	}
 }
 
-func TestRunScanFromSymlinkedWorkingDirectory(t *testing.T) {
-	// README §Database: a relative path gets the working directory, its
-	// symlinks resolved, put in front of it. With home/proj a symlink
-	// to data/proj, entered as the working directory through the
-	// symlink, ../new/db.sqlite names data/new/db.sqlite. scan must
-	// create that directory and file, and nothing beside home/proj.
-	dir, err := filepath.EvalSymlinks(t.TempDir())
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = os.MkdirAll(filepath.Join(dir, "data", "proj"), 0o750)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = os.Mkdir(filepath.Join(dir, "home"), 0o750)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = os.Symlink(filepath.Join(dir, "data", "proj"),
-		filepath.Join(dir, "home", "proj"))
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// t.Chdir also sets PWD to the path through the symlink, as a
-	// shell does after cd.
-	t.Chdir(filepath.Join(dir, "home", "proj"))
-	t.Setenv(databaseEnv, "../new/db.sqlite")
-
-	want := "scan: new database " + dir + "/data/proj/../new/db.sqlite" +
-		" (from " + databaseEnv + ")\n"
-	if got := scanOK(t, t.TempDir()); !strings.HasPrefix(got, want) {
-		t.Errorf("scan stderr = %q, want it to start %q", got, want)
-	}
-
-	_, err = os.Stat(filepath.Join(dir, "data", "new", "db.sqlite"))
-	if err != nil {
-		t.Errorf("database the path names: %v", err)
-	}
-
-	_, err = os.Lstat(filepath.Join(dir, "home", "new"))
-	if !errors.Is(err, fs.ErrNotExist) {
-		t.Errorf("home/new: stat error %v, want it missing", err)
-	}
-}
-
-func TestRunEscapesDatabasePath(t *testing.T) {
-	// README §Database: each subcommand's first line escapes the
-	// database path like the paths in a report, so a tab, newline or
-	// backslash in it keeps the line one line.
-	dir := t.TempDir()
-	t.Setenv(databaseEnv, dir+"/a\tb\nc\\d.sqlite")
-
-	escaped := dir + `/a\tb\nc\\d.sqlite`
-	from := " (from " + databaseEnv + ")\n"
-
-	want := "scan: new database " + escaped + from
-	if got := scanOK(t, t.TempDir()); !strings.HasPrefix(got, want) {
-		t.Errorf("scan stderr = %q, want it to start %q", got, want)
-	}
-
-	for _, name := range []string{cmdReport, cmdTrees} {
-		stderr := captureStderr(t)
-
-		code := run([]string{name}, io.Discard, os.Stderr)
-
-		want = name + ": database " + escaped + from
-		if got := stderr(); code != exitOK || !strings.HasPrefix(got, want) {
-			t.Errorf("run(%s) = %d with stderr %q, want %d and it to "+
-				"start %q", name, code, got, exitOK, want)
-		}
-	}
-}
-
 func TestRunNamesDefaultDatabase(t *testing.T) {
 	// README §Database: with SFDUPES_DATABASE empty, each subcommand's
 	// first line on stderr names the default database. A database may