-Basic update algorithm:
-
- 1. recurse to all of our direct dependencies and
- update their bases and tips
-
- 2. Update our base.
-
- i. Compute our base's set of desired included deps:
- The set of desired included deps for a base
- is the union of the desired included deps for each
- branch named in the base's branch's direct deps, plus
- the name of every direct external dep.
- The set of desired included deps for a branch
- is the set of desired included deps for the branch's
- base plus the branch name itself.
-
- ii. For each source in the best order, do the following merge:
- (Our base has sources:
- - the branch for each direct dep
- - the remote base
- - the topgit base, if this is a topgit import)
-
- Find the (latest) common ancestor.
-
- Check for unwanted dependency removals.
- An unwanted dependency removal is
- A branch in the desired included deps
- Which exists in the common ancestor's actual included deps
- but which is missing in the source's actual included deps
- (NB that this definition excludes dependency removals
- which have already occurred on our base; these will be
- reverted later.)
- For each unwanted dependency removal (ie for each such
- branch), search as follows:
- * An "unwanted removal commit" is a non-merge commit in the
- history of the source, which removes the dep from the
- actual included deps.
- * But the search stops at any point where we would have to
- traverse a commit where .topbloke/deps is empty (which
- stops us looking into the hitory of non-topbloke-controlled
- branches). This can be done with git-rev-list
- --remove-empty.
- * It also stops at any point where we meet a commit which
- does have the dep in the actual included deps. We have
- to do this by hand.
- * The the relevant unwanted removal commit for that dep is
- the most recent unwanted removal commit, as defined.
- Select the unwantedly removed dep whose relevant unwanted
- removal commit is the earliest. Merge from the ancestor of
- that relevant unwanted removal commit. Merge from the relevant
- unwanted removal commit using -s ours.
-
- Now continue to the next unwanted dependency removal.
-
- (The purpose of this, and the result, is that the unwanted
- dependency removal has gone away. Doing things in this order
- tries to keep the unwanted dependency removal's reversions as
- close as possible to their originating points. The
- recursion, which processes dependencies before their clients,
- tries to keep the reversion churn localised: client patches
- of a patch affected by an unwanted removal will benefit from
- that client's resolution of the situation.)
-
- If there are no (more) unwanted dependency removals, merge
- from the source.
-
- iii.
- Check whether our list of dependencies has changed. If so
- we need to restart the whole base update.
-
- iv.
- Check for missing or unwanted dependency inclusions. Compare
- our base's desired included deps with our base's actual
- included deps. In exceptional conditions, they will not
- be identical. This can happen, for example, because a
- dependency removal was incorporated into our base branch but
- the removed branch was introduced as an explicit dependency.
- This will also happen if we remove a dependency ourselves.
-
- Do the unwanted inclusions first, and then the missing ones.
- (This is because that the missing ones cannot depend on the
- unwanted ones, as otherwise the unwanted ones would be in the
- desired inclusions. So removing the unwanted ones first
- reduces the chances of conflicts.)
-
- So, repeatedly:
- * Do the comparison between desired and actual included
- * Pick a missing inclusion, or failing that an unwanted one
- (call this the "relevant" branch)
- * Depth first search all of the dependencies of the
- relevant branch; if any of these is also a missing
- (resp. unwanted) inclusion, start again processing it
- instead.
- * Attempt to apply the appropriate diff to add (resp. remove)
- the contents of the relevant patch (adjusted appropriately
- for metadata, XXX??? particularly the actual inclusion list)
- XXX if we want to add a dep we need to update the dep first
- * Go round again looking for another discrepancy.
-
- 3. Update our branch.
- Our branch has sources:
- - our base
- - the remote for our branch
- - the topgit branch, if this is a topgit import
- For each source in the best order, do the merge.
-
- Double-check the actual dependency inclusions. In
- particular, if we just upgraded to actual dependency tracking
- we may need to explicitly add our branch name to the actual
- dependency inclusion list.
-
-The "best order" for merges is in order of recency of common
-ancestor, most recent first, and if that does not distinguish,
-merging from local branches first.
-
-"Recency" refers to the order from git-rev-list --date-order.
-
-
Patch removal:
- removed patch must be removed from the deps of its
Foreign branches:
When merging from a foreign dependency, check that it
- does not have .topbloke metadata; LATER if it
- does, could produce a new commit which has .topbloke removed
- and merge from that
+ does not have .topbloke metadata
Patch naming:
needs to be globally unique
~ian / topbloke.git / blobdiff