X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=topbloke.git;a=blobdiff_plain;f=DESIGN;h=66252ceafed5073102f9118622b726f7f838af0d;hp=44650578a3d5473243481e8022e6ce395453f25e;hb=e9bcefd93e14d2d8d2906efdd713cde6be4c4fa5;hpb=c98691988623c62686b36ad0c42d4a958a306a5d diff --git a/DESIGN b/DESIGN index 4465057..66252ce 100644 --- a/DESIGN +++ b/DESIGN @@ -1,121 +1,3 @@ -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 @@ -143,9 +25,7 @@ Patch removal: 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 @@ -216,107 +96,12 @@ Strategies for each metadata file merge: in base/tip same patch & branch dep -> base base -> tip msg T textual merge rm from src not in src + patch BT must be same rm from src must be same + base T compute specially rm from src not in src deps B list merge rm from src rm from src deleted T std existence merge rm from src not in src - patch- BT must be same rm from src must be same - topgit- B std exist/text merge rm from src rm from src [^+]*- ?? textual merge rm from src rm from src +included BT list merge rm from non-tb src list merge + +ends BT compute specially compute specially +*- ?? textual merge rm from non-tb src textual merge *[^-] ?? die, aborting all ops, if found in any tb src or branch - - - - - -Unwanted removal search subgraphs: - - rm relevant removal - inc - - rm impossible to undo removal, arrgh, terminates search -inc inc.. -/ ??? \ - - rm -inc.. rm.. merge of a removal, search down the rm path -/ [inc] \ - - inc ??? call it an inclusion, terminate the search - rm - - inc merge of an inclusion, terminates search -inc.. rm.. -/ [rm] \ - - inc ??? call it an inclusion, terminate search -rm.. rm.. -/ ??? \ - - - rm inc inc rm irrelevant - rm inc inc inc.. rm rm.. - - - - OUR BASE SOURCE OUR IT TIP - | | | - | | | - ADD DEP WH/ inc rm | - NEEDS IT /| /\ | - / | rm \ | - / | ______________'/ \ | - inc |' / \ | IT tip - / inc REMOVAL rm \ | elsewhere - / | / \ | | | - / | inc \ | | | - some IT | / | | | | - | inc | | | | - / | | | | | - / inc | | | | - | / | | | | | - / / inc | | | | - / | | `------------ | ----<-------- | -.| | - / inc inc | | *2 | - | |`- | ------------- | ----<--------.| | | - | `---inc | 1* / | - | | | | / | - | RE-INCLUDE inc rm REMOVAL |' | - inc \ | | | | - | * REMOVAL rm | | | - | | / | | - |`-------------- | ----------. / | | - | | inc ANC2 | | - inc inc / | | - |`.____________ | / | | - | `inc ANC1 / | | - | | /`--------<----------- | ---. | - without inc / | \/ - | | / | / - \ RE-INCLUDE inc / | / - \ \ | / | / - \ * REMOVAL rm / | / - \ | / | / - \ inc FIRST ADD DEP |/ - \ | \ *3 - \ | `------------<-------------.| - \ | | - \ without | - \_____ | | - `without | - | | - IT - - - Merge 1* and 2*, diff against some relevant base branch commit - or something, and apply to proposed. ??? - - -After we are done: - source tip is included in our base - -Each time: - * pick common ancestor - * compute whether merge from common anc would unwantedly remove - * if so we arrange that the common anc is a "rm" but our branch - actually contains IT