Understanding Repository Corruption
In Mercurial, repository corruption can manifest in several ways, such as missing files, corrupted history, or inconsistencies in repository metadata. The critical first step is to identify the extent and impact of the corruption. Some possible signs include:
- Errors during pull, push, or update operations.
- Strange behavior during merges or when listing history.
- Missing commits or unexpected changes in the file tree.
Back Up the Current Repository State
Before attempting any repairs, make a complete backup of your existing repository. This is critical as some repair operations might result in further loss or damage. Use the command line to create a pressure-free backup:
cp -r /path/to/repo /path/to/repo_backup
Use hg verify to Diagnose the Problem
The hg verify command is invaluable in diagnosing corruption issues. It checks the integrity of the data stored in the Mercurial repository:
hg verify
This command will output any inconsistencies it finds, such as missing nodes or mismatches between changesets and manifests.
Recovering from a Bad State Using Strip
If the corruption affects recent changesets, you might recover by stripping the problematic changes using the hg strip command, provided by the mq extension. Ensure that the mq extension is enabled in your .hgrc file:
[extensions]
mq =
Use the command with caution:
hg strip -r REV
Replace REV with the revision number directly following the last known good state.
Restoring from a Bundle
If you have previously created bundles using the hg bundle command, you can restore your repository:
hg bundle /path/to/backup.bundle
hg unbundle /path/to/backup.bundle
This approach restores changesets to their previous state as of the time the bundle was created.
Re-cloning the Repository
In some cases, the easiest solution is to re-clone the repository from a remote source. Ensure that the remote has a consistent copy and re-clone to your working directory:
hg clone https://remote-repository-url /path/to/local/repo
This commands fetches a fresh copy and ensures the local repository is free from corruption, assuming the remote is clean.
Reapplying Untracked Changes
If you have uncommitted changes at the time of corruption, manually apply them to the files after restoring the repository:
# If you recovered your files separately
cp /path/to/repo_backup/yourfile.ext /path/to/local/repo/yourfile.ext
Luckily, Mercurial's hg show commands or using some tools can help to remerge with minimal loss.
Preventive Measures
Regular maintenance and vigilance go a long way in preventing future corruptions. Consider these steps:
- Regularly use `hg verify`, especially before and after critical operations.
- Maintain up-to-date backups using `hg bundle` or external tools.
- Encourage the use of clean commits and refrain from interruptions during 'push' or 'pull' operations.
By being proactive with your repository management and addressing anomalies immediately, you can mitigate risks associated with repository corruption.
