Summary:
Depends on D19779. Ref T13216. The push logs currently record the "hostWait", which is roughly "locking + subprocess cost". We also record locking separately, so we can figure out "subprocess cost" alone by subtracting the lock costs.
However, the subprocess (normally `git receive-pack`) runs hooks, and we don't have an easy way to figure out how much time was spent doing actual `git` stuff vs spent doing commit hook processing. This would have been useful in diagnosing at least one recent issue.
Track at least a rough hook cost and record it in the push logs.
Test Plan: Pushed to a repository, saw a reasonable hook cost appear in the database table.
Reviewers: amckinley
Reviewed By: amckinley
Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T13216
Differential Revision: https://secure.phabricator.com/D19780
Summary:
Depends on D19778. Ref T13216. See PHI943, PHI889, et al.
We currently have a push log and a pull log, but do not separately log intracluster synchronization events. We've encountered several specific cases where having this kind of log would be helpful:
- In PHI943, an install was accidentally aborting locks early. Having timing information in the sync log would let us identify this more quickly.
- In PHI889, an install hit an issue with `MaxStartups` configuration in `sshd`. A log would let us identify when this is an issue.
- In PHI889, I floated a "push the linux kernel + fetch timeout" theory. A sync log would let us see sync/fetch timeouts to confirm this being a problem in practice.
- A sync log will help us assess, develop, test, and monitor intracluster routing sync changes (likely those in T13211) in the future.
Some of these events are present in the pull log already, but only if they make it as far as running a `git upload-pack` subprocess (not the case with `MaxStartups` problems) -- and they can't record end-to-end timing.
No UI yet, I'll add that in a future change.
Test Plan:
- Forced all operations to synchronize by adding `|| true` to the version check.
- Pulled, got a sync log in the database.
Reviewers: amckinley
Reviewed By: amckinley
Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T13216
Differential Revision: https://secure.phabricator.com/D19779
Summary:
Ref T13109. Ref T13202. See PHI905. See PHI889. When we receive a write to a repository cluster, we currently send it to a random writable node.
Instead, we can prefer:
- the node currently holding the write lock; or
- any node which is already up to date.
These should simply be better nodes to take writes in all cases. The write lock is global for the repository, so there's no scaling benefit to spreading writes across different nodes, and these particular nodes will be able to accept the write more quickly.
Test Plan:
- This is observable by using `fprintf(STDERR, "%s\n", ...)` in the logic, then running `git push`. I'd like to pull this routing logic out of `PhabricatorRepository` at some point, probably into a dedicated `ClusterURIQuery` sort of class, but that is a larger change.
- Added some `fprintf(...)` stuff around which nodes were being selected.
- Added a `sleep(10)` after grabbing the write lock.
- In one window, pushed. Then pushed in a second window.
- Saw the second window select the lock holder as the write target based on it currently holding the lock.
- Without a concurrent push, saw pushes select up-to-date nodes based on their up-to-date-ness.
Reviewers: amckinley
Reviewed By: amckinley
Subscribers: joshuaspence, timhirsh
Maniphest Tasks: T13202, T13109
Differential Revision: https://secure.phabricator.com/D19734
Summary:
Now on the blame page, identities get `avatar.png` and there are little tooltips that show a few characters of the committer identity string.
Also add a default icon for repo identities.
Test Plan: Loaded some blame pages for files touched by users with and without repo identities attached.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D19587
Summary:
Ref T13202. See PHI889. Update the read and write locks to the modern parameterized verison, which handles hashing/normalization and can store better logs.
This parameterized mode was added in D19173 and has been used successfully for some time, but not all locks have switched over to it yet.
Test Plan:
- Added an `fprintf(STDERR, $full_name)` to the lock code.
- Pulled a repository.
- Saw sensible lock name on stdout before "acquired read lock...".
- Additional changes in this patch series will vet this more completely.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13202
Differential Revision: https://secure.phabricator.com/D19701
Summary:
Depends on D19657. Ref T13197. See PHI841.
This enriches the results from `diffusion.commit.search` with information similar to the information returned by the "commits" attachment from `differential.diff.search`.
Also include unreachable, imported, message, audit status, and repository PHID.
Test Plan: Called `diffusion.commit.search` and reviewed the results, which looked sensible.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13197
Differential Revision: https://secure.phabricator.com/D19658
Summary:
Depends on D19656. Ref T13197. See PHI851.
- This class is now a real object, so get rid of the "Constants" part of the name.
- Rename it for greater consistency with other modern objects.
- Get rid of the `MODERN_` tag now that the old constants are gone.
Test Plan: Bunch of `grep`, browsed around.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13197
Differential Revision: https://secure.phabricator.com/D19657
Summary: Depends on D19652. Ref T13197. See PHI851. This migrates the actual `auditStatus` on Commits, and older status transactions.
Test Plan:
- Ran migrations.
- Spot-checked the database for sanity.
- Ran some different queries, got unchanged results from before migration.
- Reviewed historic audit state transactions, and accepted/raised concern on new audits. All state transactions appeared to generate properly.
Reviewers: amckinley
Reviewed By: amckinley
Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T13197
Differential Revision: https://secure.phabricator.com/D19655
Summary: Ref T13197. We're almost ready to migrate: let the Query accept either older integer values or new string values. Then move some callsites to use strings.
Test Plan: Called `audit.query`, browsed audits, audited commits.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13197
Differential Revision: https://secure.phabricator.com/D19650
Summary: Ref T13195. See PHI851. Continuing down the path toward replacing these legacy numeric constants with more modern string constants.
Test Plan:
- Raised concern, requested verification, verified.
- Looked at commit hovercard with audit status.
- Viewed header on a commit page.
- (Didn't test the Doorkeeper stuff since it requires linking to Asana and seems unlikely to break.)
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13195
Differential Revision: https://secure.phabricator.com/D19647
Summary:
Ref T13195. See PHI851. Add an object, analogous to the `DifferentialRevisionStatus` object, to handle audit status management.
This will primarily make it easier to swap storage over to strings later, but also cleans things up a bit.
Test Plan: Viewed audit/commit lists, saw sensible state icons. Ran `bin/audit synchronize`, got sensible output.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13195
Differential Revision: https://secure.phabricator.com/D19646
Summary:
Fixes T12251. Ref T13189. See PHI610. The difficulty here is that we don't want to disclose Phabricator account information to Buildkite. We're comfortable disclosing information from `git`, etc.
- For commits, use the Identity to provide authorship information from Git.
- For revisions, use the local commit information on the Diff to provide the Git/Mercurial/etc author of the HEAD commit.
Test Plan:
- Built commits and revisions in Buildkite via Harbormaster.
- I can't actually figure out how to see author information on the Buildkite side, but the values look sane when dumped locally.
Reviewers: amckinley
Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T13189, T12251
Differential Revision: https://secure.phabricator.com/D19614
Summary: Ref T12164. Updates another controller to use identities.
Test Plan:
Pretty ad-hoc, but loaded the main pages of several different repos with and without repo identities. I'm not totally convinced the `author` from this data structure is actually being used:
```
$return = array(
'commit' => $modified,
'date' => $date,
'author' => $author,
'details' => $details,
);
```
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Maniphest Tasks: T12164
Differential Revision: https://secure.phabricator.com/D19580
Summary: Depends on D19582. Ref T13164. It's not possible to reach the editor without passing through a CAN_EDIT check, and it shouldn't be necessarily to manually specify that edits require CAN_EDIT by default.
Test Plan: Grepped for `RepositoryEditor`, verified that all callsites pass through a CAN_EDIT check.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13164
Differential Revision: https://secure.phabricator.com/D19583
Summary: Depends on D19491.
Test Plan: Viewed some commits where the identity was mapped to a user and another that wasn't; saw the header render either a link to the user or the identity object.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D19492
Summary: Depends on D19555. Ref T13164. See PHI765. An install is interested in getting a sense of the impact of a particular blocking rule, which seems reasonable. Support filtering for pushes blocked by a particular rule or set of rules.
Test Plan: {F5776385}
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13164
Differential Revision: https://secure.phabricator.com/D19556
Summary:
Ref T13164. See PHI765. We currently show "Rejected: Herald" in the push log UI, but don't show which rule rejected a push.
We store this data, and it's potentially useful: either for hunting down a particular issue, or for getting a general sense of how often a reject rule is triggering (maybe because you want to tune how aggressive it is).
Show this data in the web UI, and include it in the data export payload.
Test Plan:
- Pushed to a hosted repository so that I got blocked by a Herald rule.
- Viewed the push logs in the web UI, now saw which rule triggered things.
- Exported logs to CSV, saw Herald rule PHIDs in the data.
{F5776211}
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13164
Differential Revision: https://secure.phabricator.com/D19555
Summary: I landed D19491 a little aggressively, so allow this field to be null until after the migration goes out.
Test Plan: Loaded commits without identity objects; did not get any errors.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D19496
Summary: Ref T12164. Make it easier to work with identity objects by attaching them to commits and attaching users to identities.
Test Plan: Loaded some commits with `->needIdentities(true)` and checked the resulting objects.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Maniphest Tasks: T12164
Differential Revision: https://secure.phabricator.com/D19491
Summary: This never worked.
Test Plan: Ran `bin/repository rebuild-identities` and viewed identity objects with `currentEffectiveUserID`s and no longer got errors about attempting to attach `null` objects instead of `PhabricatorUser` objects.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D19495
Summary:
Ref T13151. Ref T12164. Two small tweaks:
- If we aren't actually going to change anything, just skip the writes. This makes re-running/resuming a lot faster (~20x, locally).
- Print when we touch a commit so there's some kind of visible status.
This is just a small quality-of-life tweak that I wrote anyway while investigating T13152, and will make finishing off db024, db025 and db010 manually a little easier.
Test Plan:
- Set `authorIdentityPHID` + `committerIdentityPHID` to `NULL`.
- Ran `rebuild-identities`, saw status information.
- Ran `rebuild-identiites` again, saw it go faster with status information.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13151, T12164
Differential Revision: https://secure.phabricator.com/D19484
Summary:
Depends on D19443. Creates a workflow for populating the new identity table by iterating over commits, either one repo at a time or all at once. Locally caches identities to avoid fetching them `inf` times. An actual migration that invokes this workflow will come in another revision that won't land until at least next week.
Performance is ~2k commits in 4.9s on my local machine.
Test Plan: Ran locally a few times with a few different states of the `repository_identity` table.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: jcox, Korvin, PHID-OPKG-gm6ozazyms6q6i22gyam
Differential Revision: https://secure.phabricator.com/D19446
Summary: Depends on D19429. Depends on D19423. Ref T12164. This creates new columns `authorIdentityPHID` and `committerIdentityPHID` on commit objects and starts populating them. Also adds the ability to explicitly set an Identity's assignee to "unassigned()" to null out an incorrect auto-assign. Adds more search functionality to identities. Also creates a daemon task for handling users adding new email address and attempts to associate unclaimed identities.
Test Plan: Imported some repos, watched new columns get populated. Added a new email address for a previous commit, saw daemon job run and assign the identity to the new user. Searched for identities in various and sundry ways.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin, PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T12164
Differential Revision: https://secure.phabricator.com/D19443
Summary: Depends on D19423. Ref T12164. Adds controllers capable of listing and editing `PhabricatorRepositoryIdentity` objects. Starts creating those objects when commits are parsed.
Test Plan: Reparsed some revisions, observed objects getting created in the database. Altered some `Identity` objects using the controllers and observed effects in the database. No attempts made to validate behavior under "challenging" author/committer strings.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin, PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T12164
Differential Revision: https://secure.phabricator.com/D19429
Summary: Ref T12164. Start building initial objects for managing `RepositoryIdentity` objects. This won't land until much more of the infrastructure is in place.
Test Plan: Ran `bin/storage upgrade` and observed expected table.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin, PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T12164
Differential Revision: https://secure.phabricator.com/D19423
Summary:
Ref T13124. See PHI593.
When you `arc diff` in a Git or Mercurial repository, we upload some information about the local commits in your working copy which the change was generated from.
In the future (for example, with T1508) we may increase the prominence of this feature.
Provide a stable way to read this information back via the API. This roughly mirrors the information we provide about commits in "diffusion.commit.search", although the latter is less fleshed-out today.
Test Plan: Used `differential.diff.search` to retrieve commit information about Git, Mercurial, and Subversion diffs. (There's no info for Subversion, but it doesn't crash or anything.)
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13124
Differential Revision: https://secure.phabricator.com/D19386
Summary:
Depends on D19356. Fixes T10883. Ref T13120.
- Add a "writable" property to the bindings, defaulting to "true" with a nice dropdown.
- When selecting hosts, allow callers to request a writable host.
- If the caller wants a writable host, only return hosts if they're writable.
- In SVN and Mercurial, we sometimes return only writable hosts when we //could// return read-only hosts, but figuring out if these request are read-only or read-write is currently tricky. Since these repositories can't really cluster yet, this shouldn't matter too much today.
Test Plan:
- Without any config changes, viewed repositories via web UI and pushed/pulled via SSH and HTTP.
- Made all nodes in the cluster read-only by disabling "writable", pulled and hit the web UI (worked), tried to push via SSH and HTTP (got errors about read-only).
- Put everything back, pulled and pushed.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13120, T10883
Differential Revision: https://secure.phabricator.com/D19357
Summary:
Depends on D19355. Ref T10883. Ref T13120. Rather than adding a million parameters here, wrap the selector-parameters in an `$options`.
The next change adds a new "writable" option to support forcing selection of writable hosts.
Test Plan: Pulled and pushed via HTTP and SSH, viewed repositories via Diffusion.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13120, T10883
Differential Revision: https://secure.phabricator.com/D19356
Summary: Ref T13105. This needs refinement but blame sort of works again, now.
Test Plan: Viewed files in Diffusion and Files; saw blame in Diffusion when viewing in source mode.
Reviewers: mydeveloperday
Reviewed By: mydeveloperday
Maniphest Tasks: T13105
Differential Revision: https://secure.phabricator.com/D19309
Summary:
Ref T13105. This breaks about 9,000 features but moves Diffusion to DocumentEngine for rendering. See T13105 for a more complete list of all the broken stuff.
But you can't bake a software without breaking all the features every time you make a change, right?
Test Plan: Viewed various files in Diffusion, used DocumentEngine features like highlighting and rendering engine selection.
Reviewers: mydeveloperday
Reviewed By: mydeveloperday
Subscribers: mydeveloperday
Maniphest Tasks: T13105
Differential Revision: https://secure.phabricator.com/D19302
Summary:
Depends on D19280. Ref T13110. Although Harbormaster cares about all builds, Differential does not practically care about local lint and unit results in determining build status.
In Differential, orient publishing around "remote builds" instead of "builds".
This does not yet change any of the draft logic, it just makes the timeline story use newer logic.
Test Plan: Used `bin/harbormaster publish` (with some guard-clause removal) to publish some buildables to revisions without anything crashing.
Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T13110
Differential Revision: https://secure.phabricator.com/D19281
Summary:
Ref T13110. Currently, build status is published the same way for every Buildable by the BuildEngine.
I want to change this to delegate publishing to each Buildable, particularly so that Differential may use more detailed rules for handling builds and drafts.
Rather than add additional methods to the existing `BuildableInterface`, add an engine generator method instead. This is a pattern which has seen more use recently (e.g., in Ferret) and lets us pay a little more upfront to pull complex pieces of logic out of the main class and let them use inheritence more easily. If we had Traits that might cover this to some degree.
I'd expect to eventually reduce the size of `BuildableInterface` and move the `CircleCI` and `BuildKite` interfaces so that the `BuildableEngine` implements them instead of the main object.
Here, this new engine does nothing and is never instantiated. In upcoming changes, publishing logic will move into it so that Differential can handle publishing differently.
Test Plan: Ran `arc liberate`, loaded pages, grepped for `BuildableInterface`.
Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T13110
Differential Revision: https://secure.phabricator.com/D19278
Summary:
Ref T13114. See PHI514. This makes some attempt to undo the damage caused by incorrectly publishing a repository.
Don't run this.
Test Plan: Yikes.
Maniphest Tasks: T13114
Differential Revision: https://secure.phabricator.com/D19271
Summary:
Depends on D19249. Ref T13109. Add timing information to the `PushEvent`:
- `writeWait`: Time spent waiting for a write lock.
- `readWait`: Time spent waiting for a read lock.
- `hostWait`: Roughly, total time spent on the leaf node.
The primary goal here is to see if `readWait` is meaningful in the wild. If it is, that motivates smarter routing, and the value of smarter routing can be demonstrated by looking for a reduction in read wait times.
Test Plan: Pushed some stuff, saw reasonable timing values in the table. Saw timing information in "Export Data".
Maniphest Tasks: T13109
Differential Revision: https://secure.phabricator.com/D19250
Summary:
Depends on D19247. Ref T13109. When we receive an SSH request, generate a random unique ID for the request. Then thread it down through the process tree.
The immediate goal is to let the `ssh-exec` process coordinate with `commit-hook` process and log information about read and write lock wait times. Today, there's no way for `ssh-exec` to interact with the `PushEvent`, but this is the most helpful place to store this data for users.
Test Plan: Made pushes, saw the `PushEvent` table populate with a random request ID. Exported data and saw the ID preserved in the export.
Maniphest Tasks: T13109
Differential Revision: https://secure.phabricator.com/D19249
Summary:
Ref T13109. Make it slightly more clear what the scope of the write and read locks are, and slightly more clear that we're actively acquiring locks, not just sitting around waiting.
While waiting on another writer, show who we're waiting on so you can walk over to their desk and glare at them.
Test Plan:
Added `sleep(15)` after `willWrite()`. Pushed in two windows. Saw new, more informative messages. In the second window, saw the new guidance:
> # Waiting for hector to finish writing (on device "repo1.local.phacility.net" for 11s)...
Reviewers: asherkin
Reviewed By: asherkin
Subscribers: asherkin
Maniphest Tasks: T13109
Differential Revision: https://secure.phabricator.com/D19247
Summary: See PHI432. Ref T13099. Short names never made it to the UI/API but seem stable now, so support them.
Test Plan: {F5465173}
Maniphest Tasks: T13099
Differential Revision: https://secure.phabricator.com/D19202
Summary:
Ref T13096. Currently, we do a fair amount of clever digesting and string manipulation to build lock names which are less than 64 characters long while still being reasonably readable.
Instead, do more of this automatically. This will let lock acquisition become simpler and make it more possible to build a useful lock log.
Test Plan: Ran `bin/repository update`, saw a reasonable lock acquire and release.
Maniphest Tasks: T13096
Differential Revision: https://secure.phabricator.com/D19173
Summary: Depends on D19028. Ref T13053. Fixes T6576. An HTML body was built here, but not passed to the actual mail message.
Test Plan: Will verify production push mail.
Maniphest Tasks: T13053, T6576
Differential Revision: https://secure.phabricator.com/D19029
Summary:
Depends on D19019. Ref T13053. Fixes T12689. See PHI178.
Currently, if `@alice` resigns from a revision but `#alice-fan-club` is still a subscriber or reviewer, she'll continue to get mail. This is undesirable.
When users are associated with an object but have explicitly disengaged in an individal role (currently, only resign in audit/differential) mark them "unexpandable", so that they can no longer be included through implicit membership in a group (a project or package).
`@alice` can still get mail if she's a explicit recipient: as an author, owner, or if she adds herself back as a subscriber.
Test Plan:
- Added `@ducker` and `#users-named-ducker` as reviewers. Ducker got mail.
- Resigned as ducker, stopped getting future mail.
- Subscribed explicitly, got mail again.
- (Plus some `var_dump()` sanity checking in the internals.)
Reviewers: amckinley
Maniphest Tasks: T13053, T12689
Differential Revision: https://secure.phabricator.com/D19021
Summary:
Depends on D19009. Ref T13053. For "Must Encrypt" mail, we must currently strip the "Thread-Topic" header because it sometimes contains sensitive information about the object.
I don't actually know if this header is useful or anyting uses it. My understanding is that it's an Outlook/Exchange thing, but we also implement "Thread-Index" which I think is what Outlook/Exchange actually look at. This header may have done something before we implemented "Thread-Index", or maybe never done anything. Or maybe older versions of Excel/Outlook did something with it and newer versions don't, or do less. So it's possible that an even better fix here would be to simply remove this, but I wasn't able to convince myself of that after Googling for 10 minutes and I don't think it's worth hours of installing Exchange/Outlook to figure out. Instead, I'm just trying to simplify our handling of this header for now, and maybe some day we'll learn more about Exchange/Outlook and can remove it.
In a number of cases we already use the object monogram or PHID as a "Thread-Topic" without users ever complaining, so I think that if this header is useful it probably isn't shown to users, or isn't shown very often (e.g., only in a specific "conversation" sub-view?). Just use the object PHID (which should be unique and stable) as a thread-topic, everywhere, automatically.
Then allow this header through for "Must Encrypt" mail.
Test Plan: Processed some local mail, saw object PHIDs for "Thread-Topic" headers.
Reviewers: amckinley
Maniphest Tasks: T13053
Differential Revision: https://secure.phabricator.com/D19012
Summary:
Ref T13053. Adds revision stamps (status, reviewers, etc). Adds Herald rule stamps, like the existing X-Herald-Rules header.
Removes the "self" stamps, since you can just write a rule against `whatever(@epriestley)` equivalently. If there's routing logic around this, it can live in the routing layer. This avoids tons of self-actor, self-mention, self-reviewer, self-blocking-reviewer, self-resigned-reviewer, etc., stamps.
Use `natcasesort()` instead of `sort()` so that numeric values (like monograms) sort `9, 80, 700` instead of `700, 80, 9`.
Remove the commas from rendering since they don't really add anything.
Test Plan: Edited tasks and revisions, looked at mail stamps, saw stamps that looked pretty reasonable (with no more self stuff, no more commas, sorting numbers, and Herald stamps).
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13053
Differential Revision: https://secure.phabricator.com/D18997
Summary:
Ref T13057. This makes "reverts" syntax more visible and useful. In particular, you can now `Reverts Dxx` in a revision or commit, and `Reverts <hash>` from a revision.
When you do, the corresponding object will get a more-visible cross-reference marker in its timeline:
{F5405517}
From here, we can look at surfacing revert information more heavily, since we can now query it on revision/commit pages via edges.
Test Plan: Used "reverts <hash>" and "reverts <revision>" in Differential and Diffusion, got sensible results in the timeline.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13057
Differential Revision: https://secure.phabricator.com/D18978
