268
260
sooner you can stop evaluating the 99% that you don't care about, the
269
261
less work you do.
272
Avoiding work: avoiding reading parent data
273
-------------------------------------------
275
We would like to avoid the work of reading any data about the parent
276
revisions. We should at least try to avoid reading anything from the
277
repository; we can also consider whether it is possible or useful to hold
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less parent information in the working tree.
280
When a commit of selected files is requested, the committed snapshot is a
281
composite of some directories from the parent revision and some from the
282
working tree. In this case it is logically necessary to have the parent
283
inventory information.
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If file last-change information or per-file graph information is stored
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then it must be available from the parent trees.
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If the Branch's storage method does delta compression at commit time it
289
may need to retrieve file or inventory texts from the repository.
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It is desirable to avoid roundtrips to the Repository during commit,
292
particularly because it may be remote. If the WorkingTree can determine
293
by itself that a text was in the parent and therefore should be in the
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Repository that avoids one roundtrip per file.
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There is a possibility here that the parent revision is not stored, or not
297
correctly stored, in the repository the tree is being committed into, and
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so the committed tree would not be reconstructable. We could check that
299
the parent revision is present in the inventory and rely on the invariant
300
that if a revision is present, everything to reconstruct it will be
307
Caller starts a commit
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>>> Branch.commit(from_tree, options)
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This creates a CommitBuilder object matched to the Branch, Repository and
312
Tree. It can vary depending on model differences or by knowledge of what
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is efficient with the Repository and Tree. Model differences might
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include whether no-text-change merges need to be reported, and whether the
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The basic CommitBuilder.commit structure can be
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1. Ask the branch if it is ready to commit (up to date with master if
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2. Ask the tree if it is ready to commit to the branch (up to date with
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branch?), no conflicts, etc
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3. Commit changed files; prototype implementation:
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a. Ask the working tree for all committable files; for each it should
327
return the per-file parents, stat information, kind, etc.
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b. Ask the repository to store the new file text; the repository should
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return the stored sha1 and new revision id.
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4. Commit changed inventory
334
5. Commit revision object
344
Complications of commit
345
-----------------------
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Bazaar (as of 0.17) does not support selective-file commit of a merge;
348
this could be done if we decide how it should be recorded - is this to be
349
stored as an overall merge revision; as a preliminary non-merge revisions;
350
or will the per-file graph diverge from the revision graph.
352
There are several checks that may cause the commit to be refused, which
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may be activated or deactivated by options.
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* presence of conflicts in the tree
357
* presence of unknown files
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* the working tree basis is up to date with the branch tip
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* the local branch is up to date with the master branch, if there
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is one and --local is not specified
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* an empty commit message is given,
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* a hook flags an error
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* a "pointless" commit, with no inventory changes
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Most of these require walking the tree and can be easily done while
371
recording the tree shape. This does require that it be possible to abort
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the commit after the tree changes have been recorded. It could be ok to
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either leave the unreachable partly-committed records in the repository,
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* when automatically adding new files or deleting missing files during
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commit, they must be noted during commit and written into the working
382
* refuse "pointless" commits with no file changes - should be easy by
383
just refusing to do the final step of storing a new overall inventory
386
* heuristic detection of renames between add and delete (out of scope for
389
* pushing changes to a master branch if any
391
* running hooks, pre and post commit
393
* prompting for a commit message if necessary, including a list of the
394
changes that have already been observed
396
* if there are tree references and recursing into them is enabled, then
399
Commit needs to protect against duplicated file ids
402
Updates that need to be made in the working tree, either on conclusion
403
of commit or during the scan, include
405
* Changes made to the tree shape, including automatic adds, renames or
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* For trees (eg dirstate) that cache parent inventories, the old parent
409
information must be removed and the new one inserted
411
* The tree hashcache information should be updated to reflect the stat
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value at which the file was the same as the committed version, and the
413
content hash it was observed to have. This needs to be done carefully to
414
prevent inconsistencies if the file is modified during or shortly after
415
the commit. Perhaps it would work to read the mtime of the file before we
416
read its text to commit.
422
The commit api is invoked by the command interface, and copies information
423
from the tree into the branch and its repository, possibly updating the
424
WorkingTree afterwards.
426
The command interface passes:
428
* a commit message (from an option, if any),
429
* or an indication that it should be read interactively from the ui object;
430
* a list of files to commit
431
* an option for a dry-run commit
432
* verbose option, or callback to indicate
433
* timestamp, timezone, committer, chosen revision id
435
* option for local-only commit on a bound branch
436
* option for strict commits (fail if there are unknown or missing files)
437
* option to allow "pointless" commits (with no tree changes)
439
(This is rather a lot of options to pass individually and just for code tidyness maybe some of them should be combine into objects.)
441
>>> Branch.commit(from_tree, message, files_to_commit, ...)
443
There will be different implementations of this for different Branch
444
classes, whether for foreign branches or Bazaar repositories using
445
different storage methods.
447
Most of the commit should occur during a single lockstep iteration across
448
the workingtree and parent trees. The WorkingTree interface needs to
449
provide methods that give commit all it needs. Some of these methods
450
(such as answering the file's last change revision) may be deprecated in
451
newer working trees and there we have a choice of either calculating the
452
value from the data that is present, or refusing to support commit to
455
For a dirstate tree the iteration of changes from the parent can easily be
456
done within its own iter_changes.
458
Dirstate inventories may be most easily updated in a single operation at
459
the end; however it may be best to accumulate data as we proceed through
460
the tree rather than revisiting it at the end.
462
Showing a progress bar for commit may not be necessary if we report files
463
as they are committed. Alternatively we could transiently show a progress
464
bar for each directory that's scanned, even if no changes are observed.
466
This needs to collect a list of added/changed/removed files, each of which
467
must have its text stored (if any) and containing directory updated. This
468
can be done by calling Tree._iter_changes on the source tree, asking for
471
In the 0.17 model the commit operation needs to know the per-file parents
472
and per-file last-changed revision.
474
(In this and other operations we must avoid having multiple layers walk
475
over the tree separately. For example, it is no good to have the Command
476
layer walk the tree to generate a list of all file ids to commit, because
477
the tree will also be walked later. The layers that do need to operate
478
per-file should probably be bound together in a per-dirblock iterator,
479
rather than each iterating independently.)
481
Branch->Tree interface
482
----------------------
484
The Branch commit code needs to ask the Tree what should be committed, in
485
terms of changes from the parent revisions. If the Tree holds all the
486
necessary parent tree information itself it can do it single handed;
487
otherwise it may need to ask the Repository for parent information.
489
This should be a streaming interface, probably like iter_changes returning
490
information per directory block.
492
The interface should not return a block for directories that are
493
recursively unchanged.
495
The tree's idea of what is possibly changed may be more conservative than
496
that of the branch. For example the tree may report on merges of files
497
where the text is identical to the parents: this must be recorded for
498
Bazaar branches that record per-file ancestry but is not necessary for all
499
branches. If the tree is responsible for determining when directories
500
have been recursively modified then it will report on all the parents of
501
such files. There are several implementation options:
503
1. Return all files and directories the branch might want to commit, even
504
if the branch ends up taking no action on them.
506
2. When starting the iteration, the branch can specify what type of change
507
is considered interesting.
509
Since these types of changes are probably (??) rare compared to files that
510
are either completely unmodified or substantially modified, the first may
511
be the best and simplest option.
513
The branch needs to build an inventory to commit, which must include
514
unchanged files within changed directories. This should be returned from
515
the working tree too. Repositories that store per-directory inventories
516
will want to build and store these from the lowest directories up.
517
For 0.17 format repositories with an all-in-one inventory it may be
518
easiest to accumulate inventory entries in arbitrary order into an
519
in-memory Inventory and then serialize it.
521
It ought to be possible to commit any Tree into a Branch, without
522
requiring a WorkingTree; the commit code should cope if the tree is not
523
interested in updating hashcache information or does not have a
527
Information from the tree to repository
528
---------------------------------------
530
The main things the tree needs to tell the Branch about are:
532
* A file is modified from its parent revision (in text, permissions,
533
other), and so its text may need to be stored.
535
Files should also be reported if they have more than one unique parent
536
revision, for repositories that store per-file graphs or last-change
537
revisions. Perhaps this behaviour should be optional.
539
**XXX:** are renames/deletions reported here too?
541
* The complete contents of a modified directory, so that its inventory
542
text may be stored. This should be done after all the contained files
543
and directories have been reported. If there are unmodified files,
544
or unselected files carried through from
546
XXX: Actually perhaps not grouped by directory, but rather grouped
547
appropriately for the shape of inventory storage in the repository.
549
In a zoomed-in checkout the workingtree may not have all the shape data
552
* A file is missing -- could cause either automatic removal or an aborted
555
* Any unknown files -- can cause automatic addition, abortion of a strict
556
commit, or just reporting.
559
Information from the repository to the tree
560
-------------------------------------------
562
After the commit the tree needs to be updated to the new revision. Some
563
information which was accumulated during the commit must be made available
564
to the workingtree. It's probably reasonable to hold it all in memory and
565
allow the workingtree to get it in whatever order it wants.
567
* A list of modified entries, and for each one:
569
* The stat values observed when the file was first read.
571
* The hash of the committed file text.
573
* The file's last-change revision, if appropriate.
575
This should include any entries automatically added or removed.
577
This might be construed as an enhanced version of ``set_parent_trees``.
578
We can avoid a stat on each file by using the value that was observed when
586
For a partial commit the directory contents may need to contain a mix of
587
entries from the working tree and parent trees. This code probably
588
shouldn't live in a specific tree implementation; maybe there should be a
589
general filter that selects paths from one tree into another?
591
However, the tree walking code does probably need to know about selected
592
paths to avoid examining unselected files or directories.
594
We never refuse selective file commits (except of merges).
601
What is common to all commit implementations, regardless of workingtree or
604
* Prompting for a commit message?
605
* Strictness/conflict checks?
608
How should this be separated?
615
For current and contemplated Bazaar storage formats, we can only finally
616
commit a directory after its contained files and directories have been
619
The dirstate workingtree format naturally iterates by directory in order
620
by path, yielding directories before their contents. This may also be the
621
most efficient order in which to stat and read the files.
623
One option would be to construe the interface as a visitor which reports
624
when files are detected to be changed, and also when directories are
628
Open question: per-file graphs
629
------------------------------
631
**XXX:** If we want to retain explicitly stored per-file graphs, it would
632
seem that we do need to record per-file parents. We have not yet finally
633
settled that we do want to remove them or treat them as a cache. This api
634
stack is still ok whether we do or not, but the internals of it may
added
removed
doc/developers/performance-commit.txt
