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by_commit_with_notes v2 #39

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44 changes: 44 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,42 @@ That means Limmat won't re-run tests unless the actual repository contents
change - for example changes to the commit message won't invalidate cache
results.

For fine-grained cache control, you can use `cache = "by_commit_with_notes"`.
This creates cache keys based on both the commit hash and git notes attached
to the commit under the `refs/notes/limmat` ref. This allows you to
invalidate the cache for specific commits by adding or modifying notes:

```bash
# This will invalidate the cache for this commit
git notes --ref=limmat add -m "force rebuild" abc1234

# Different note content = different cache key
git notes --ref=limmat add -m "test with flag X" abc1234 --force
```

Your test scripts can access the exact notes content that was used for the cache key:

```bash
#!/bin/bash
# Example test script using git notes for configuration

if [[ -n "$LIMMAT_NOTES_OBJECT" ]]; then
# Get the exact notes content used for cache key generation
notes_content=$(git cat-file -p "$LIMMAT_NOTES_OBJECT")
echo "Test configuration from notes: $notes_content"

# Parse test parameters from notes
if echo "$notes_content" | grep -q "rebuild"; then
echo "Force rebuild requested"
make clean
fi
else
echo "No notes attached to this commit, using defaults"
fi

make test
```
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@bjackman bjackman Sep 21, 2025

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Rework the docs.


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@bjackman bjackman Sep 22, 2025

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Need to integrate it into limmat test

If the test is terminated by a signal, it isn't considered to have produced a
result: instead of "success" or "failure" it's an "error". Errors aren't cached.

Expand Down Expand Up @@ -323,6 +359,7 @@ These environment variables are passed to your job.
| `LIMMAT_ORIGIN` | Path of the main repository worktree (i.e. `--repo`). |
| `LIMMAT_COMMIT` | Hash of the commit to be tested. |
| `LIMMAT_CONFIG` | Path of the config file. |
| `LIMMAT_NOTES_OBJECT` | Git object hash of the notes content used for cache key generation (when using `cache = "by_commit_with_notes"`). Empty if no notes exist. |
| `LIMMAT_RESOURCE_<resource_name>_<n>` | Values for [resources](#resources) used by the test. |
| `LIMMAT_RESOURCE_<resource_name>` | If the test only uses one of a resource, shorthand for `LIMMAT_RESOURCE_<resource_name>_0` |
| `LIMMAT_ARTIFACTS_<job_name>` | If the test depends on `job_name`, this directory contains that job's [artifacts](#artifacts). |
Expand Down Expand Up @@ -376,6 +413,13 @@ make -j defconfig
make -j16 vmlinux O=$LIMMAT_ARTIFACTS
"""

# Run stress tests that can be configured via git notes
[[tests]]
name = "stress_test"
cache = "by_commit_with_notes"
command = "stress_test.sh"
depends_on = ["kbuild"]

# Check the locally-built kernel boots in a QEMU VM.
[[tests]]
name = "boot_qemu"
Expand Down
4 changes: 3 additions & 1 deletion limmat.schema.json
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Expand Up @@ -32,7 +32,8 @@
"enum": [
"no_caching",
"by_commit",
"by_tree"
"by_tree",
"by_commit_with_notes"
]
},
"Command": {
Expand Down Expand Up @@ -103,6 +104,7 @@
],
"properties": {
"cache": {
"description": "Controls when test results are cached. \"by_commit\" (default) caches by commit hash. \"by_tree\" caches by tree hash (ignores commit message changes). \"by_commit_with_notes\" caches by commit hash plus git notes under refs/notes/limmat. \"no_caching\" disables caching.",
"default": "by_commit",
"allOf": [
{
Expand Down
1 change: 1 addition & 0 deletions src/config.rs
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Expand Up @@ -94,6 +94,7 @@ pub struct Test {
/// willing to wait when you terminate this program.
shutdown_grace_period_s: u64,
#[serde(default = "default_cache_policy")]
/// Controls when test results are cached. "by_commit" (default) caches by commit hash. "by_tree" caches by tree hash (ignores commit message changes). "by_commit_with_notes" caches by commit hash plus git notes under refs/notes/limmat. "no_caching" disables caching.
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@bjackman bjackman Sep 21, 2025

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Document on the enum

cache: CachePolicy,
#[serde(default)]
depends_on: Vec<String>,
Expand Down
68 changes: 67 additions & 1 deletion src/git.rs
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Expand Up @@ -172,6 +172,7 @@ impl Worktree for PersistentWorktree {
pub struct Commit {
pub hash: CommitHash,
pub tree: TreeHash,
pub limmat_notes_object: Option<Hash>,
}

impl Commit {
Expand All @@ -180,6 +181,7 @@ impl Commit {
Self {
hash: CommitHash::new("080b8ecbad3e34e55c5a035af80100f73b742a8d"),
tree: TreeHash::new("6366d790125291272542a6b40f6fd3400e080821"),
limmat_notes_object: None,
}
}
}
Expand Down Expand Up @@ -457,6 +459,65 @@ pub trait Worktree: Debug + Sync {
})
}

async fn get_notes_object_hash(
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@bjackman bjackman Sep 21, 2025

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Document. Make notes ref configurable.

&self,
commit_hash: &CommitHash,
) -> anyhow::Result<Option<Hash>> {
debug!(
"Looking for git notes for commit {}",
commit_hash.as_ref() as &str
);
let output = self
.git(["notes", "--ref=limmat", "list"])
.await
.arg(commit_hash.as_ref() as &str)
.output()
.await
.context("failed to run 'git notes list'")?;

debug!("git notes list exit code: {:?}", output.status.code());
debug!(
"git notes list stdout: {:?}",
String::from_utf8_lossy(&output.stdout)
);
debug!(
"git notes list stderr: {:?}",
String::from_utf8_lossy(&output.stderr)
);
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@bjackman bjackman Sep 21, 2025

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Let's remove most or all of the debug logs in here.


// Exit code 1 means no notes found, which is fine
if output.status.code() == Some(1) {
debug!("No notes found for commit {}", commit_hash.as_ref() as &str);
return Ok(None);
}

if !output.status.success() {
// Other error - treat as no notes to be safe
debug!(
"git notes list failed with code {:?}, treating as no notes",
output.status.code()
);
return Ok(None);
}

let notes_output = String::from_utf8_lossy(&output.stdout);
let notes_object_hash = notes_output.trim();
if notes_object_hash.is_empty() {
debug!(
"Empty notes output for commit {}",
commit_hash.as_ref() as &str
);
return Ok(None);
}
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@bjackman bjackman Sep 21, 2025

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Let's treat empty output as an error here too


debug!(
"Found notes object hash {} for commit {}",
notes_object_hash,
commit_hash.as_ref() as &str
);
Ok(Some(Hash::new(notes_object_hash.to_string())))
}

// None means we successfully looked it up but it didn't exist.
async fn rev_parse<S>(&self, rev_spec: S) -> anyhow::Result<Option<Commit>>
where
Expand Down Expand Up @@ -486,9 +547,14 @@ pub trait Worktree: Debug + Sync {
String::from_utf8_lossy(&output.stderr)
);
}

let commit_hash = CommitHash::new(parts[0]);
let limmat_notes_object = self.get_notes_object_hash(&commit_hash).await?;

Ok(Some(Commit {
hash: CommitHash::new(parts[0]),
hash: commit_hash,
tree: TreeHash::new(parts[1]),
limmat_notes_object,
}))
}
}
Expand Down
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