> > Of course, --ignore-ancestry will also, well ignore ancestry,
> > and only do a diff. So, if you have a file with the same name
> > as an earlier file with the same path/name that is not
> > actually its parent you are going to get a bad merge.
>
> Sorry, I'm a bit lost here. Could you explain this maybe with an
> example?
I think the best bet is to quote from the redbook:
Using --ignore-ancestry
If this option is passed to svn merge, it causes the merging logic to
mindlessly generate differences the same way that svn diff does, ignoring any
historical relationships. We discuss this later in the chapter in the section
called "Noticing or Ignoring Ancestry".
Noticing or Ignoring Ancestry
When conversing with a Subversion developer, you might very likely hear
reference to the term ancestry. This word is used to describe the relationship
between two objects in a repository: if they're related to each other, one
object is said to be an ancestor of the other.
For example, suppose you commit revision 100, which includes a change to a file
foo.c. Then fo...@99 is an "ancestor" of fo...@100. On the other hand, suppose
you commit the deletion of foo.c in revision 101, and then add a new file by
the same name in revision 102. In this case, fo...@99 and fo...@102 may appear
to be related (they have the same path), but in fact are completely different
objects in the repository. They share no history or "ancestry."
The reason for bringing this up is to point out an important difference between
svn diff and svn merge. The former command ignores ancestry, while the latter
command is quite sensitive to it. For example, if you asked svn diff to compare
revisions 99 and 102 of foo.c, you would see line-based diffs; the diff command
is blindly comparing two paths. But if you asked svn merge to compare the same
two objects, it would notice that they're unrelated and first attempt to delete
the old file, then add the new file; the output would indicate a deletion
followed by an add:
D foo.c
A foo.c
Most merges involve comparing trees that are ancestrally related to one
another; therefore, svn merge defaults to this behavior.
---
It goes on to talk about merging unrelated trees which is when you would
probably want to use --ignore-ancestry.
BOb
