英文:
how to revert cabal update on a different computer
问题
task 1: 在B机器上查看当前的 hackage 状态。
task 2: 在A机器上强制执行 cabal update 到与B机器相同的状态。
英文:
I needed to compile a Haskell program an machine A which failed (for the cryptonite bug, which is not the issue here) but compiled on machine B. The difference was, that I had run cabal update on A but not on B recently. I was compiling with an older state of hackage on B than on A.
To fix the issue I need to
task 1: see which state of hackage I have on B.
task 2: force a cabal update to the same state on A.
I tried to find the required commands with cabal update -h and with search on the web, but could not identify them (and had to revert to use stack lts to progress).
what are the commands for task 1 and 2? with these commands, I could use cabal in a more controlled way and avoid surprises when some package in hackage breaks.
I am using linux (Debian 5.10.179-1 Debian 5.10.179-1) with
cabal --version
cabal-install version 3.6.2.0
compiled using version 3.6.2.0 of the Cabal library
答案1
得分: 3
虽然我不知道有一个特定的命令来查询时间戳，但有几种方法可以让 cabal 显示它。可能最不侵入性的一种方法是使用 cabal list 命令并启用详细输出：
$ cabal -v --installed list base
读取来自 hackage.haskell.org 的可用软件包...
使用截止到 2022-12-25T11:36:12Z 的历史状态（从最近的指定）
cabal update
索引状态（hackage.haskell.org）= 2022-12-25T11:36:12Z（HEAD = 2023-06-08T09:48:09Z）
* base
简介：基础库
默认可用版本：4.17.0.0
已安装版本：4.17.0.0
许可证：BSD-3-Clause
一旦您获得了所需的时间戳，您可以在另一台计算机上使用 cabal update 命令时指定它：
$ cabal update 'hackage.haskell.org,2022-12-25T11:36:12Z'
从 hackage.haskell.org 下载最新的软件包列表
hackage.haskell.org 的软件包列表已经是最新的。
索引状态已设置为 2022-12-25T11:36:12Z。
要恢复到以前的状态，请运行：
cabal v2-update 'hackage.haskell.org,2023-06-08T09:48:09Z'
由于 cabal update 命令会打印旧的索引时间戳，找到时间戳的另一种方法是进行更新，记录下旧的时间戳，然后立即将其恢复。不过，这比只读方法更繁琐一些。
英文:
While I don't know of a command to specifically query the timestamp, there are a few ways of getting cabal to display it. The least invasive one is possibly using cabal list with verbose output:
$ cabal -v --installed list base
Reading available packages of hackage.haskell.org...
Using historical state as of 2022-12-25T11:36:12Z specified from most recent
cabal update
index-state(hackage.haskell.org) = 2022-12-25T11:36:12Z (HEAD =
2023-06-08T09:48:09Z)
* base
Synopsis: Basic libraries
Default available version: 4.17.0.0
Installed versions: 4.17.0.0
License: BSD-3-Clause
Once you have the desired timestamp, you can specify it when using cabal update in the other computer:
$ cabal update 'hackage.haskell.org,2022-12-25T11:36:12Z'
Downloading the latest package list from hackage.haskell.org
Package list of hackage.haskell.org is up to date.
The index-state is set to 2022-12-25T11:36:12Z.
To revert to previous state run:
cabal v2-update 'hackage.haskell.org,2023-06-08T09:48:09Z'
Since cabal update prints the old index timestamp, another option to find the timestamp would be updating, jotting down the old timestamp, and immediately reverting it. That's a bit more of a hassle than a read-only method, though.
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