https://github.com/cpg314/mtime-rewind

Rewind the mtime of files whose mtime advanced since the last execution without a content change.
https://github.com/cpg314/mtime-rewind

cache cache-invalidation cargo mtime rust

Last synced: 1 day ago
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Rewind the mtime of files whose mtime advanced since the last execution without a content change.

• Host: GitHub
• URL: https://github.com/cpg314/mtime-rewind
• Owner: cpg314
• License: apache-2.0
• Created: 2023-09-03T08:01:46.000Z (about 1 year ago)
• Default Branch: main
• Last Pushed: 2024-05-04T09:43:21.000Z (7 months ago)
• Last Synced: 2024-05-04T10:33:31.873Z (7 months ago)
• Topics: cache, cache-invalidation, cargo, mtime, rust
• Language: Rust
• Homepage:
• Size: 12.7 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE-MIT

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README

        
# mtime-rewind

Rewind the `mtime` attribute of files whose modification advanced since the last execution without a content change.

This is useful to avoid unnecessary cache invalidations in systems using `mtime` to detect changes, for example [Rust's cargo](https://doc.rust-lang.org/cargo/) (see [this issue](https://github.com/rust-lang/cargo/issues/6529)).

More generally, see the [`mtime` comparison considered harmful blog post](https://apenwarr.ca/log/20181113).

## Usage

```console

$ mtime-rewind

Rewind the mtime of files whose mtime advanced since the last execution without a content change

Usage: mtime-rewind [OPTIONS] 

Arguments:

  

Options:

      --dry   Do not edit only mtime, only list the changes that would be made

  -h, --help  Print help

```

- The first execution will store hashes and modification times of files in a `.hashprint` file at the root. Hidden files and [cache directories](https://bford.info/cachedir/) are ignored.

- Subsequent executions will rewind files that have not changed to the previous modification time, and update the modification times of other files if necessary.

Typically, `mtime-rewind` can be executed as the first step of a CI build.

## Example

```console

$ mtime-rewind ~/project

[INFO mtime_rewind] Computing hashes...

[INFO mtime_rewind] Computed hashes for 9 files

[INFO mtime_rewind] Writing hashes for the first time...

[INFO mtime_rewind] Wrote "/root/project/.hashprint"

[INFO mtime_rewind] Done

$ touch src/main.rs

[INFO mtime_rewind] Computing hashes...

[INFO mtime_rewind] Computed hashes for 9 files

[INFO mtime_rewind] Restoring modification times for unchanged files...

[INFO mtime_rewind] Loading cached state...

[INFO mtime_rewind] Loaded hashes for 9 files

[INFO mtime_rewind] Rewinding "/root/project/src/main.rs" from SystemTime { tv_sec: 1693727396, tv_nsec: 146042169 } to SystemTime { tv_sec: 1693727019, tv_nsec: 668108072 } as its contents did not change

[INFO mtime_rewind] 1 files rewinded

[INFO mtime_rewind] Saving the new state...

[INFO mtime_rewind] Wrote "/root/project/.hashprint"

[INFO mtime_rewind] Done

```