Bisecting: Difference between revisions

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* <code>git bisect start</code> flag [https://git-scm.com/docs/git-bisect#Documentation/git-bisect.txt---first-parent <code>--first-parent</code>]: select merge commits, which depending on the repository can help for caching as well as commit stability.

* [https://~~git~~.~~qyliss.net~~/hydrasect~~/about/~~ <code>hydrasect</code>]: select cached commits cached by Hydra~~, useful for bisecting nixpkgs. After each checkout run <code>git checkout $(hydrasect-search | head -1)</code>.~~

* [https://github.com/blitz/hydrasect <code>hydrasect</code>]: select cached commits cached by Hydra

* [https://github.com/symphorien/nixpkgs-staging-bisecter <code>nixpkgs-staging-bisecter</code>] ~~(<code>nix-build</code> only)~~: reduce number of derivations to be built.

* [https://github.com/symphorien/nixpkgs-staging-bisecter <code>nixpkgs-staging-bisecter</code>]: reduce number of derivations to be built.

== Automating bisects ==

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* [https://github.com/timokau/nix-bisect <code>nix-bisect</code>]: helps better judge outcome (<code>git bisect</code>'s <code>good</code> vs <code>bad</code> <code>skip</code>) and gives nicer outputs than <code>git bisect run</code>.

== ~~Flakes~~ ==

=== Bisecting dependencies ===

~~Bisecting~~ changes in a ~~[[flake]]~~ itself can ~~just follow~~ the regular bisecting ~~process.~~

While for regressions from changes in a Nix project itself we can bisect following the regular process, bisecting regression in dependencies is a bit different in the sense the repository you would build is separate from the repository you are bisecting.

~~Bisecting regressions~~ in ~~flakes' inputs~~ is a bit different in the sense the ~~repositories~~ you ~~are building~~ is ~~not~~ the repository you are bisecting. In this ~~case you can use:~~

One can do this by running a bisect from a local checkout of the dependency that induced the regression.

* <code>--override-input</code>~~: nix flag~~ that ~~enables bisecting flakes~~' ~~inputs~~

==== Bisecting inputs of [[Flakes|Flake]] projects ====

* <code>--flake</code> flag ~~on nix operations~~: ~~allows overriding~~ flake directory ~~so you can use nix flake operations from e.g~~. <code>git bisect run</code>

For dependencies managed using Flakes, such a <code>bisect run</code> can be used with Nix Flake commands' flag <code>--override-input</code> to override specific inputs to use the bisected dependency in its inputs.

Using <code>git bisect run</code> from your local checkout of the dependency that caused the regression, the flake directory to run a command for can be overridden for a NixOS configuration, for example, using [[nixos-rebuild]]'s <code>--flake</code> flag. If we can reproduce the issue using a <code>dry-build</code>, this might then look like: <code>git bisect run nixos-rebuild dry-build --override-input $DEPENDENCY_NAME $(pwd) --flake <NIXOS_CONFIG_DIR>#<FLAKE_ATTRIBUTE></code>.

For a regular Nix Flake project, we do not have a command flag like [[nixos-rebuild]]'s <code>--flake</code> to specify the directory of your project. We might then address this by wrapping the Nix command in a script changing directory there, for example using: <code>git bisect run sh -c "cd <PROJECT_DIR>; nix flake check --override-input <DEPENDENCY_NAME> $(pwd)"</code>.

[[Category:Version control]]

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 * <code>git bisect start</code> flag [https://git-scm.com/docs/git-bisect#Documentation/git-bisect.txt---first-parent <code>--first-parent</code>]: select merge commits, which depending on the repository can help for caching as well as commit stability.
-* [https://git.qyliss.net/hydrasect/about/ <code>hydrasect</code>]: select cached commits cached by Hydra, useful for bisecting nixpkgs. After each checkout run <code>git checkout $(hydrasect-search | head -1)</code>.
+* [https://github.com/blitz/hydrasect <code>hydrasect</code>]: select cached commits cached by Hydra
-* [https://github.com/symphorien/nixpkgs-staging-bisecter <code>nixpkgs-staging-bisecter</code>] (<code>nix-build</code> only): reduce number of derivations to be built.
+* [https://github.com/symphorien/nixpkgs-staging-bisecter <code>nixpkgs-staging-bisecter</code>]: reduce number of derivations to be built.
 == Automating bisects ==
@@ Line 14: / Line 14: @@
 * [https://github.com/timokau/nix-bisect <code>nix-bisect</code>]: helps better judge outcome (<code>git bisect</code>'s <code>good</code> vs <code>bad</code> <code>skip</code>) and gives nicer outputs than <code>git bisect run</code>.
-== Flakes ==
+=== Bisecting dependencies ===
-Bisecting changes in a [[flake]] itself can just follow the regular bisecting process.
+While for regressions from changes in a Nix project itself we can bisect following the regular process, bisecting regression in dependencies is a bit different in the sense the repository you would build is separate from the repository you are bisecting.
-Bisecting regressions in flakes' inputs is a bit different in the sense the repositories you are building is not the repository you are bisecting. In this case you can use:
+One can do this by running a bisect from a local checkout of the dependency that induced the regression.
-* <code>--override-input</code>: nix flag that enables bisecting flakes' inputs
+==== Bisecting inputs of [[Flakes|Flake]] projects ====
-* <code>--flake</code> flag on nix operations: allows overriding flake directory so you can use nix flake operations from e.g. <code>git bisect run</code>
+For dependencies managed using Flakes, such a <code>bisect run</code> can be used with Nix Flake commands' flag <code>--override-input</code> to override specific inputs to use the bisected dependency in its inputs.
+Using <code>git bisect run</code> from your local checkout of the dependency that caused the regression, the flake directory to run a command for can be overridden for a NixOS configuration, for example, using [[nixos-rebuild]]'s <code>--flake</code> flag. If we can reproduce the issue using a <code>dry-build</code>, this might then look like: <code>git bisect run nixos-rebuild dry-build --override-input $DEPENDENCY_NAME $(pwd) --flake <NIXOS_CONFIG_DIR>#<FLAKE_ATTRIBUTE></code>.
+For a regular Nix Flake project, we do not have a command flag like [[nixos-rebuild]]'s <code>--flake</code> to specify the directory of your project. We might then address this by wrapping the Nix command in a script changing directory there, for example using: <code>git bisect run sh -c "cd <PROJECT_DIR>; nix flake check --override-input <DEPENDENCY_NAME> $(pwd)"</code>.
 [[Category:Version control]]