view tests/test-ui-verbosity.py.out @ 23702:c48924787eaa

filectx.parents: enforce changeid of parent to be in own changectx ancestors

Because of the way filenodes are computed, you can have multiple changesets
"introducing" the same file revision. For example, in the changeset graph
below, changeset 2 and 3 both change a file -to- and -from- the same content.

  o 3: content = new
  |
  | o 2: content = new
  |/
  o 1: content = old

In such cases, the file revision is create once, when 2 is added, and just reused
for 3. So the file change in '3' (from "old" to "new)" has no linkrev pointing
to it).  We'll call this situation "linkrev-shadowing". As the linkrev is used for
optimization purposes when walking a file history, the linkrev-shadowing
results in an unexpected jump to another branch during such a walk.. This leads to
multiple bugs with log, annotate and rename detection.

One element to fix such bugs is to ensure that walking the file history sticks on
the same topology as the changeset's history. For this purpose, we extend the
logic in 'basefilectx.parents' so that it always defines the proper changeset
to associate the parent file revision with. This "proper" changeset has to be an
ancestor of the changeset associated with the child file revision.

This logic is performed in the '_adjustlinkrev' function. This function is
given the starting changeset and all the information regarding the parent file
revision. If the linkrev for the file revision is an ancestor of the starting
changeset, the linkrev is valid and will be used. If it is not, we detected a
topological jump caused by linkrev shadowing, we are going to walk the
ancestors of the starting changeset until we find one setting the file to the
revision we are trying to create.

The performance impact appears acceptable:

- We are walking the changelog once for each filelog traversal (as there should
  be no overlap between searches),

- changelog traversal itself is fairly cheap, compared to what is likely going
  to be perform on the result on the filelog traversal,

- We only touch the manifest for ancestors touching the file, And such
  changesets are likely to be the one introducing the file. (except in
  pathological cases involving merge),

- We use manifest diff instead of full manifest unpacking to check manifest
  content, so it does not involve applying multiple diffs in most case.

- linkrev shadowing is not the common case.

Tests for fixed issues in log, annotate and rename detection have been
added.

But this changeset does not solve all problems. It fixes -ancestry-
computation, but if the linkrev-shadowed changesets is the starting one, we'll
still get things wrong. We'll have to fix the bootstrapping of such operations
in a later changeset. Also, the usage of `hg log FILE`  without --follow still
has issues with linkrev pointing to hidden changesets, because it relies on the
`filelog` revset which implement its own traversal logic that is still to be
fixed.

Thanks goes to:
- Matt Mackall: for nudging me in the right direction
- Julien Cristau and Rémi Cardona: for keep telling me linkrev bug were an
  evolution show stopper for 3 years.
- Durham Goode: for finding a new linkrev issue every few weeks
- Mads Kiilerich: for that last rename bug who raise this topic over my
  anoyance limit.

      hgrc settings    command line options      final result   
    quiet verbo debug   quiet verbo debug      quiet verbo debug
 0  False False False   False False False  ->  False False False
 1   True False False   False False False  ->   True False False
 2  False  True False   False False False  ->  False  True False
 3   True  True False   False False False  ->  False False False
 4  False False  True   False False False  ->  False  True  True
 5   True False  True   False False False  ->  False  True  True
 6  False  True  True   False False False  ->  False  True  True
 7   True  True  True   False False False  ->  False  True  True
 8  False False False    True False False  ->   True False False
 9   True False False    True False False  ->   True False False
10  False  True False    True False False  ->   True False False
11   True  True False    True False False  ->   True False False
12  False False  True    True False False  ->   True False False
13   True False  True    True False False  ->   True False False
14  False  True  True    True False False  ->   True False False
15   True  True  True    True False False  ->   True False False
16  False False False   False  True False  ->  False  True False
17   True False False   False  True False  ->  False  True False
18  False  True False   False  True False  ->  False  True False
19   True  True False   False  True False  ->  False  True False
20  False False  True   False  True False  ->  False  True False
21   True False  True   False  True False  ->  False  True False
22  False  True  True   False  True False  ->  False  True False
23   True  True  True   False  True False  ->  False  True False
24  False False False    True  True False  ->  False False False
25   True False False    True  True False  ->  False False False
26  False  True False    True  True False  ->  False False False
27   True  True False    True  True False  ->  False False False
28  False False  True    True  True False  ->  False False False
29   True False  True    True  True False  ->  False False False
30  False  True  True    True  True False  ->  False False False
31   True  True  True    True  True False  ->  False False False
32  False False False   False False  True  ->  False  True  True
33   True False False   False False  True  ->  False  True  True
34  False  True False   False False  True  ->  False  True  True
35   True  True False   False False  True  ->  False  True  True
36  False False  True   False False  True  ->  False  True  True
37   True False  True   False False  True  ->  False  True  True
38  False  True  True   False False  True  ->  False  True  True
39   True  True  True   False False  True  ->  False  True  True
40  False False False    True False  True  ->  False  True  True
41   True False False    True False  True  ->  False  True  True
42  False  True False    True False  True  ->  False  True  True
43   True  True False    True False  True  ->  False  True  True
44  False False  True    True False  True  ->  False  True  True
45   True False  True    True False  True  ->  False  True  True
46  False  True  True    True False  True  ->  False  True  True
47   True  True  True    True False  True  ->  False  True  True
48  False False False   False  True  True  ->  False  True  True
49   True False False   False  True  True  ->  False  True  True
50  False  True False   False  True  True  ->  False  True  True
51   True  True False   False  True  True  ->  False  True  True
52  False False  True   False  True  True  ->  False  True  True
53   True False  True   False  True  True  ->  False  True  True
54  False  True  True   False  True  True  ->  False  True  True
55   True  True  True   False  True  True  ->  False  True  True
56  False False False    True  True  True  ->  False  True  True
57   True False False    True  True  True  ->  False  True  True
58  False  True False    True  True  True  ->  False  True  True
59   True  True False    True  True  True  ->  False  True  True
60  False False  True    True  True  True  ->  False  True  True
61   True False  True    True  True  True  ->  False  True  True
62  False  True  True    True  True  True  ->  False  True  True
63   True  True  True    True  True  True  ->  False  True  True