Get rid of "must not start with ." logic

It serves very little purpose and isn't even correct as-is.

README.md

@@ -156,8 +156,7 @@ OPTIONS
     --error-file <string>, $GITSYNC_ERROR_FILE
             The path to an optional file into which errors will be written.
             This may be an absolute path or a relative path, in which case it
-            is relative to --root.  If it is relative to --root, the first path
+            is relative to --root.
-            element may not start with a period.
 
     --exechook-backoff <duration>, $GITSYNC_EXECHOOK_BACKOFF
             The time to wait before retrying a failed --exechook-command.  If
@@ -235,11 +234,10 @@ OPTIONS
             The path to at which to create a symlink which points to the
             current git directory, at the currently synced hash.  This may be
             an absolute path or a relative path, in which case it is relative
-            to --root.  The last path element is the name of the link and must
+            to --root.  Consumers of the synced files should always use this
-            not start with a period.  Consumers of the synced files should
+            link - it is updated atomically and should always be valid.  The
-            always use this link - it is updated atomically and should always
+            basename of the target of the link is the current hash.  If not
-            be valid.  The basename of the target of the link is the current
+            specified, this defaults to the leaf dir of --repo.
-            hash.  If not specified, this defaults to the leaf dir of --repo.
 
     --man
             Print this manual and exit.
@@ -325,8 +323,7 @@ OPTIONS
     --touch-file <string>, $GITSYNC_TOUCH_FILE
             The path to an optional file which will be touched whenever a sync
             completes.  This may be an absolute path or a relative path, in
-            which case it is relative to --root.  If it is relative to --root,
+            which case it is relative to --root.
-            the first path element may not start with a period.
 
     --username <string>, $GITSYNC_USERNAME
             The username to use for git authentication (see --password-file or

cmd/git-sync/main.go

@@ -544,10 +544,6 @@ func main() {
 		*flVerbose = *flDeprecatedV
 	}
 	log := func() *logging.Logger {
-		if strings.HasPrefix(*flErrorFile, ".") {
-			fmt.Fprintf(os.Stderr, "ERROR: --error-file may not start with '.'\n")
-			os.Exit(1)
-		}
 		dir, file := makeAbsPath(*flErrorFile, absRoot).Split()
 		return logging.New(dir, file, *flVerbose)
 	}()
@@ -597,9 +593,6 @@ func main() {
 		parts := strings.Split(strings.Trim(*flRepo, "/"), "/")
 		*flLink = parts[len(parts)-1]
 	}
-	if strings.HasPrefix(filepath.Base(*flLink), ".") {
-		handleConfigError(log, true, "ERROR: --link must not start with '.'")
-	}
 
 	if *flDeprecatedWait != 0 {
 		// Back-compat
@@ -647,12 +640,6 @@ func main() {
 		*flMaxFailures = *flDeprecatedMaxSyncFailures
 	}
 
-	if *flTouchFile != "" {
-		if strings.HasPrefix(*flTouchFile, ".") {
-			handleConfigError(log, true, "ERROR: --touch-file may not start with '.'")
-		}
-	}
-
 	if *flDeprecatedSyncHookCommand != "" {
 		// Back-compat
 		log.V(0).Info("setting --exechook-command from deprecated --sync-hook-command")
@@ -2301,8 +2288,7 @@ OPTIONS
     --error-file <string>, $GITSYNC_ERROR_FILE
             The path to an optional file into which errors will be written.
             This may be an absolute path or a relative path, in which case it
-            is relative to --root.  If it is relative to --root, the first path
+            is relative to --root.
-            element may not start with a period.
 
     --exechook-backoff <duration>, $GITSYNC_EXECHOOK_BACKOFF
             The time to wait before retrying a failed --exechook-command.  If
@@ -2387,11 +2373,10 @@ OPTIONS
             The path to at which to create a symlink which points to the
             current git directory, at the currently synced hash.  This may be
             an absolute path or a relative path, in which case it is relative
-            to --root.  The last path element is the name of the link and must
+            to --root.  Consumers of the synced files should always use this
-            not start with a period.  Consumers of the synced files should
+            link - it is updated atomically and should always be valid.  The
-            always use this link - it is updated atomically and should always
+            basename of the target of the link is the current hash.  If not
-            be valid.  The basename of the target of the link is the current
+            specified, this defaults to the leaf dir of --repo.
-            hash.  If not specified, this defaults to the leaf dir of --repo.
 
     --man
             Print this manual and exit.
@@ -2484,8 +2469,7 @@ OPTIONS
     --touch-file <string>, $GITSYNC_TOUCH_FILE
             The path to an optional file which will be touched whenever a sync
             completes.  This may be an absolute path or a relative path, in
-            which case it is relative to --root.  If it is relative to --root,
+            which case it is relative to --root.
-            the first path element may not start with a period.
 
     --username <string>, $GITSYNC_USERNAME
             The username to use for git authentication (see --password-file or

test_e2e.sh

@@ -2661,30 +2661,6 @@ function e2e::export_error_abs_path() {
     )
 }
 
-##############################################
-# Test export-error with invalid path
-##############################################
-function e2e::export_error_invalid_file() {
-    echo "$FUNCNAME" > "$REPO/file"
-    git -C "$REPO" commit -qam "$FUNCNAME"
-
-    (
-        set +o errexit
-        GIT_SYNC \
-            --repo="file://$REPO" \
-            --root="$ROOT" \
-            --link="link" \
-            --error-file=".error.json"
-        RET=$?
-        if [[ "$RET" != 1 ]]; then
-            fail "expected exit code 1, got $RET"
-        fi
-        assert_file_absent "$ROOT/link"
-        assert_file_absent "$ROOT/link/file"
-        assert_file_absent "$ROOT/.error.json"
-    )
-}
-
 ##############################################
 # Test touch-file
 ##############################################
@@ -2793,30 +2769,6 @@ function e2e::touch_file_abs_path() {
     assert_file_absent "$ROOT/dir/touch.file"
 }
 
-##############################################
-# Test touch-file with invalid path
-##############################################
-function e2e::touch_file_invalid_file() {
-    echo "$FUNCNAME" > "$REPO/file"
-    git -C "$REPO" commit -qam "$FUNCNAME"
-
-    (
-        set +o errexit
-        GIT_SYNC \
-            --repo="file://$REPO" \
-            --root="$ROOT" \
-            --link="link" \
-            --touch-file=".touch.file"
-        RET=$?
-        if [[ "$RET" != 1 ]]; then
-            fail "expected exit code 1, got $RET"
-        fi
-        assert_file_absent "$ROOT/link"
-        assert_file_absent "$ROOT/link/file"
-        assert_file_absent "$ROOT/.touch.file"
-    )
-}
-
 ##############################################
 # Test github HTTPS
 # TODO: it would be better if we set up a local HTTPS server