comparison tests/test-graft.t @ 42055:b9e5f3853a97

tests: better document the graft copy case

Differential Revision: https://phab.mercurial-scm.org/D6190

42054:399ed3e86a49

Graft from behind a move or rename
==================================

NOTE: This is affected by issue5343, and will need updating when it's fixed

Possible cases during a regular graft (when ca is between cta and c2):

name | c1<-cta | cta<->ca | ca->c2
A.0  |         |          |
A.1  |    X    |          |
A.2  |         |     X    |

incomplete rename into a divergence.
Finally, A.6 records a divergence entirely in the c2 pass.

A.4 has a degenerate case a<-b<-a->a, where checkcopies isn't needed at all.
A.5 has a special case a<-b<-b->a, which is treated like a<-b->a in a merge.
A.6 has a special case a<-a<-b->a. Here, checkcopies will find a spurious
incomplete divergence, which is in fact complete. This is handled later in
mergecopies.
A.7 has 4 special cases: a<-b<-a->b (the "ping-pong" case), a<-b<-c->b,
a<-b<-a->c and a<-b<-c->a. Of these, only the "ping-pong" case is interesting,

42055:b9e5f3853a97

Graft from behind a move or rename
==================================

NOTE: This is affected by issue5343, and will need updating when it's fixed

Consider this topology for a regular graft:

o c1
|
| o c2
| |
| o ca # stands for "common ancestor"
|/
o cta # stands for "common topological ancestor"

Note that in issue5343, ca==cta.

The following table shows the possible cases. Here, "x->y" and, equivalently,
"y<-x", where x is an ancestor of y, means that some copy happened from x to y.

name | c1<-cta | cta<->ca | ca->c2
A.0  |         |          |
A.1  |    X    |          |
A.2  |         |     X    |

incomplete rename into a divergence.
Finally, A.6 records a divergence entirely in the c2 pass.

A.4 has a degenerate case a<-b<-a->a, where checkcopies isn't needed at all.
A.5 has a special case a<-b<-b->a, which is treated like a<-b->a in a merge.
A.5 has issue5343 as a special case.
TODO: add test coverage for A.5
A.6 has a special case a<-a<-b->a. Here, checkcopies will find a spurious
incomplete divergence, which is in fact complete. This is handled later in
mergecopies.
A.7 has 4 special cases: a<-b<-a->b (the "ping-pong" case), a<-b<-c->b,
a<-b<-a->c and a<-b<-c->a. Of these, only the "ping-pong" case is interesting,