Mercurial > hg
view tests/test-help-hide.t @ 46607:e9901d01d135
revlog: add a mechanism to verify expected file position before appending
If someone uses `hg debuglocks`, or some non-hg process writes to the .hg
directory without respecting the locks, or if the repo's on a networked
filesystem, it's possible for the revlog code to write out corrupted data.
The form of this corruption can vary depending on what data was written and how
that happened. We are in the "networked filesystem" case (though I've had users
also do this to themselves with the "`hg debuglocks`" scenario), and most often
see this with the changelog. What ends up happening is we produce two items
(let's call them rev1 and rev2) in the .i file that have the same linkrev,
baserev, and offset into the .d file, while the data in the .d file is appended
properly. rev2's compressed_size is accurate for rev2, but when we go to
decompress the data in the .d file, we use the offset that's recorded in the
index file, which is the same as rev1, and attempt to decompress
rev2.compressed_size bytes of rev1's data. This usually does not succeed. :)
When using inline data, this also fails, though I haven't investigated why too
closely. This shows up as a "patch decode" error. I believe what's happening
there is that we're basically ignoring the offset field, getting the data
properly, but since baserev != rev, it thinks this is a delta based on rev
(instead of a full text) and can't actually apply it as such.
For now, I'm going to make this an optional component and default it to entirely
off. I may increase the default severity of this in the future, once I've
enabled it for my users and we gain more experience with it. Luckily, most of my
users have a versioned filesystem and can roll back to before the corruption has
been written, it's just a hassle to do so and not everyone knows how (so it's a
support burden). Users on other filesystems will not have that luxury, and this
can cause them to have a corrupted repository that they are unlikely to know how
to resolve, and they'll see this as a data-loss event. Refusing to create the
corruption is a much better user experience.
This mechanism is not perfect. There may be false-negatives (racy writes that
are not detected). There should not be any false-positives (non-racy writes that
are detected as such). This is not a mechanism that makes putting a repo on a
networked filesystem "safe" or "supported", just *less* likely to cause
corruption.
Differential Revision: https://phab.mercurial-scm.org/D9952
author | Kyle Lippincott <spectral@google.com> |
---|---|
date | Wed, 03 Feb 2021 16:33:10 -0800 |
parents | bb3a5c0df06b |
children | da4e6d7a8fdd |
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Test hiding some commands (which also happens to hide an entire category). $ hg --config help.hidden-command.clone=true \ > --config help.hidden-command.init=true help Mercurial Distributed SCM list of commands: Remote repository management: incoming show new changesets found in source outgoing show changesets not found in the destination paths show aliases for remote repositories pull pull changes from the specified source push push changes to the specified destination serve start stand-alone webserver Change creation: commit commit the specified files or all outstanding changes Change manipulation: backout reverse effect of earlier changeset graft copy changes from other branches onto the current branch merge merge another revision into working directory Change organization: bookmarks create a new bookmark or list existing bookmarks branch set or show the current branch name branches list repository named branches phase set or show the current phase name tag add one or more tags for the current or given revision tags list repository tags File content management: annotate show changeset information by line for each file cat output the current or given revision of files copy mark files as copied for the next commit diff diff repository (or selected files) grep search for a pattern in specified files Change navigation: bisect subdivision search of changesets heads show branch heads identify identify the working directory or specified revision log show revision history of entire repository or files Working directory management: add add the specified files on the next commit addremove add all new files, delete all missing files files list tracked files forget forget the specified files on the next commit purge removes files not tracked by Mercurial remove remove the specified files on the next commit rename rename files; equivalent of copy + remove resolve redo merges or set/view the merge status of files revert restore files to their checkout state root print the root (top) of the current working directory shelve save and set aside changes from the working directory status show changed files in the working directory summary summarize working directory state unshelve restore a shelved change to the working directory update update working directory (or switch revisions) Change import/export: archive create an unversioned archive of a repository revision bundle create a bundle file export dump the header and diffs for one or more changesets import import an ordered set of patches unbundle apply one or more bundle files Repository maintenance: manifest output the current or given revision of the project manifest recover roll back an interrupted transaction verify verify the integrity of the repository Help: config show combined config settings from all hgrc files help show help for a given topic or a help overview version output version and copyright information additional help topics: Mercurial identifiers: filesets Specifying File Sets hgignore Syntax for Mercurial Ignore Files patterns File Name Patterns revisions Specifying Revisions urls URL Paths Mercurial output: color Colorizing Outputs dates Date Formats diffs Diff Formats templating Template Usage Mercurial configuration: config Configuration Files environment Environment Variables extensions Using Additional Features flags Command-line flags hgweb Configuring hgweb merge-tools Merge Tools pager Pager Support Concepts: bundlespec Bundle File Formats glossary Glossary phases Working with Phases subrepos Subrepositories Miscellaneous: deprecated Deprecated Features internals Technical implementation topics scripting Using Mercurial from scripts and automation (use 'hg help -v' to show built-in aliases and global options) Test hiding some topics. $ hg --config help.hidden-topic.deprecated=true \ > --config help.hidden-topic.internals=true \ > --config help.hidden-topic.scripting=true help Mercurial Distributed SCM list of commands: Repository creation: clone make a copy of an existing repository init create a new repository in the given directory Remote repository management: incoming show new changesets found in source outgoing show changesets not found in the destination paths show aliases for remote repositories pull pull changes from the specified source push push changes to the specified destination serve start stand-alone webserver Change creation: commit commit the specified files or all outstanding changes Change manipulation: backout reverse effect of earlier changeset graft copy changes from other branches onto the current branch merge merge another revision into working directory Change organization: bookmarks create a new bookmark or list existing bookmarks branch set or show the current branch name branches list repository named branches phase set or show the current phase name tag add one or more tags for the current or given revision tags list repository tags File content management: annotate show changeset information by line for each file cat output the current or given revision of files copy mark files as copied for the next commit diff diff repository (or selected files) grep search for a pattern in specified files Change navigation: bisect subdivision search of changesets heads show branch heads identify identify the working directory or specified revision log show revision history of entire repository or files Working directory management: add add the specified files on the next commit addremove add all new files, delete all missing files files list tracked files forget forget the specified files on the next commit purge removes files not tracked by Mercurial remove remove the specified files on the next commit rename rename files; equivalent of copy + remove resolve redo merges or set/view the merge status of files revert restore files to their checkout state root print the root (top) of the current working directory shelve save and set aside changes from the working directory status show changed files in the working directory summary summarize working directory state unshelve restore a shelved change to the working directory update update working directory (or switch revisions) Change import/export: archive create an unversioned archive of a repository revision bundle create a bundle file export dump the header and diffs for one or more changesets import import an ordered set of patches unbundle apply one or more bundle files Repository maintenance: manifest output the current or given revision of the project manifest recover roll back an interrupted transaction verify verify the integrity of the repository Help: config show combined config settings from all hgrc files help show help for a given topic or a help overview version output version and copyright information additional help topics: Mercurial identifiers: filesets Specifying File Sets hgignore Syntax for Mercurial Ignore Files patterns File Name Patterns revisions Specifying Revisions urls URL Paths Mercurial output: color Colorizing Outputs dates Date Formats diffs Diff Formats templating Template Usage Mercurial configuration: config Configuration Files environment Environment Variables extensions Using Additional Features flags Command-line flags hgweb Configuring hgweb merge-tools Merge Tools pager Pager Support Concepts: bundlespec Bundle File Formats glossary Glossary phases Working with Phases subrepos Subrepositories (use 'hg help -v' to show built-in aliases and global options)