The pipeline used to skip a second installer only when it advertised
capabilities the first had already provided, so a hook with a different
capability still ran on the very same project. file-dedupe was installed
through pip and then again through `make install`, whose first line upgrades
pip; PEP 668 refuses that, and the run went red on a repository that was
already installed correctly.
One hook now installs a repository and the pipeline stops there. The order of
INSTALLERS is the preference: `make install` leads, because it is the hook a
repository writes for itself, while the others infer an installation from a
manifest.
A hook that fails installed nothing, so the rule is one *successful*
installation rather than one attempt: _run_installer returns a bool instead of
re-raising, and the caller moves on to the next hook. To keep that fallback
from turning a broken repository into a silent pass, a repository whose hooks
all fail now exits with the list of what was tried.
The capability bookkeeping the old skip rule needed is gone from the pipeline;
discover_capabilities remains on BaseInstaller and is now unused there.
Verified: 14 targeted unit and integration tests, and a full `pkgmgr update
--all` sweep in the arch image with 0 installation failures. Delta measured at
the consumer: repositories left without a CLI entry point, 16 before and 16
after, diff identical.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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