正如下面的timeline所示，我忘记了add之前的commit并产生了两个签入... 4a和... 3d。然后检出... 97，重复更改并用--allow-fork提交... 85。如何摆脱签到... 4a和... 3d？
user@PC:~/blinky$ fossil timeline
=== 2019-11-18 ===
17:00:08 [199f536985] *CURRENT* Move LED functions to BSP (user: user tags: trunk)
16:45:55 [b44070073d] Move LED functions to BSP (user: user tags: trunk)
16:44:03 [8e1bd6364a] Move LED functions to BSP (user: user tags: trunk)
15:35:02 [b9c7685997] *FORK* blah blah
15:16:11 [d1629aa3fa] Initial commit (user: user tags: trunk)
14:39:08 [7fe2388931] initial empty check-in (user: user tags: trunk)
+++ no more data (6) +++
PS ：偶然发现Rebase Considered Harmful，解释了“清除历史记录”的缺点。