diff options
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/commit-graph.txt | 22 | ||||
| -rw-r--r-- | Documentation/technical/directory-rename-detection.txt | 115 | ||||
| -rw-r--r-- | Documentation/technical/pack-protocol.txt | 4 | ||||
| -rw-r--r-- | Documentation/technical/protocol-v2.txt | 28 |
4 files changed, 145 insertions, 24 deletions
diff --git a/Documentation/technical/commit-graph.txt b/Documentation/technical/commit-graph.txt index e1a883eb46..c664acbd76 100644 --- a/Documentation/technical/commit-graph.txt +++ b/Documentation/technical/commit-graph.txt @@ -118,9 +118,6 @@ Future Work - The commit graph feature currently does not honor commit grafts. This can be remedied by duplicating or refactoring the current graft logic. -- The 'commit-graph' subcommand does not have a "verify" mode that is - necessary for integration with fsck. - - After computing and storing generation numbers, we must make graph walks aware of generation numbers to gain the performance benefits they enable. This will mostly be accomplished by swapping a commit-date-ordered @@ -130,25 +127,6 @@ Future Work - 'log --topo-order' - 'tag --merged' -- Currently, parse_commit_gently() requires filling in the root tree - object for a commit. This passes through lookup_tree() and consequently - lookup_object(). Also, it calls lookup_commit() when loading the parents. - These method calls check the ODB for object existence, even if the - consumer does not need the content. For example, we do not need the - tree contents when computing merge bases. Now that commit parsing is - removed from the computation time, these lookup operations are the - slowest operations keeping graph walks from being fast. Consider - loading these objects without verifying their existence in the ODB and - only loading them fully when consumers need them. Consider a method - such as "ensure_tree_loaded(commit)" that fully loads a tree before - using commit->tree. - -- The current design uses the 'commit-graph' subcommand to generate the graph. - When this feature stabilizes enough to recommend to most users, we should - add automatic graph writes to common operations that create many commits. - For example, one could compute a graph on 'clone', 'fetch', or 'repack' - commands. - - A server could provide a commit graph file as part of the network protocol to avoid extra calculations by clients. This feature is only of benefit if the user is willing to trust the file, because verifying the file is correct diff --git a/Documentation/technical/directory-rename-detection.txt b/Documentation/technical/directory-rename-detection.txt new file mode 100644 index 0000000000..1c0086e287 --- /dev/null +++ b/Documentation/technical/directory-rename-detection.txt @@ -0,0 +1,115 @@ +Directory rename detection +========================== + +Rename detection logic in diffcore-rename that checks for renames of +individual files is aggregated and analyzed in merge-recursive for cases +where combinations of renames indicate that a full directory has been +renamed. + +Scope of abilities +------------------ + +It is perhaps easiest to start with an example: + + * When all of x/a, x/b and x/c have moved to z/a, z/b and z/c, it is + likely that x/d added in the meantime would also want to move to z/d by + taking the hint that the entire directory 'x' moved to 'z'. + +More interesting possibilities exist, though, such as: + + * one side of history renames x -> z, and the other renames some file to + x/e, causing the need for the merge to do a transitive rename. + + * one side of history renames x -> z, but also renames all files within + x. For example, x/a -> z/alpha, x/b -> z/bravo, etc. + + * both 'x' and 'y' being merged into a single directory 'z', with a + directory rename being detected for both x->z and y->z. + + * not all files in a directory being renamed to the same location; + i.e. perhaps most the files in 'x' are now found under 'z', but a few + are found under 'w'. + + * a directory being renamed, which also contained a subdirectory that was + renamed to some entirely different location. (And perhaps the inner + directory itself contained inner directories that were renamed to yet + other locations). + + * combinations of the above; see t/t6043-merge-rename-directories.sh for + various interesting cases. + +Limitations -- applicability of directory renames +------------------------------------------------- + +In order to prevent edge and corner cases resulting in either conflicts +that cannot be represented in the index or which might be too complex for +users to try to understand and resolve, a couple basic rules limit when +directory rename detection applies: + + 1) If a given directory still exists on both sides of a merge, we do + not consider it to have been renamed. + + 2) If a subset of to-be-renamed files have a file or directory in the + way (or would be in the way of each other), "turn off" the directory + rename for those specific sub-paths and report the conflict to the + user. + + 3) If the other side of history did a directory rename to a path that + your side of history renamed away, then ignore that particular + rename from the other side of history for any implicit directory + renames (but warn the user). + +Limitations -- detailed rules and testcases +------------------------------------------- + +t/t6043-merge-rename-directories.sh contains extensive tests and commentary +which generate and explore the rules listed above. It also lists a few +additional rules: + + a) If renames split a directory into two or more others, the directory + with the most renames, "wins". + + b) Avoid directory-rename-detection for a path, if that path is the + source of a rename on either side of a merge. + + c) Only apply implicit directory renames to directories if the other side + of history is the one doing the renaming. + +Limitations -- support in different commands +-------------------------------------------- + +Directory rename detection is supported by 'merge' and 'cherry-pick'. +Other git commands which users might be surprised to see limited or no +directory rename detection support in: + + * diff + + Folks have requested in the past that `git diff` detect directory + renames and somehow simplify its output. It is not clear whether this + would be desirable or how the output should be simplified, so this was + simply not implemented. Further, to implement this, directory rename + detection logic would need to move from merge-recursive to + diffcore-rename. + + * am + + git-am tries to avoid a full three way merge, instead calling + git-apply. That prevents us from detecting renames at all, which may + defeat the directory rename detection. There is a fallback, though; if + the initial git-apply fails and the user has specified the -3 option, + git-am will fall back to a three way merge. However, git-am lacks the + necessary information to do a "real" three way merge. Instead, it has + to use build_fake_ancestor() to get a merge base that is missing files + whose rename may have been important to detect for directory rename + detection to function. + + * rebase + + Since am-based rebases work by first generating a bunch of patches + (which no longer record what the original commits were and thus don't + have the necessary info from which we can find a real merge-base), and + then calling git-am, this implies that am-based rebases will not always + successfully detect directory renames either (see the 'am' section + above). merged-based rebases (rebase -m) and cherry-pick-based rebases + (rebase -i) are not affected by this shortcoming, and fully support + directory rename detection. diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt index 7fee6b780a..508a344cf1 100644 --- a/Documentation/technical/pack-protocol.txt +++ b/Documentation/technical/pack-protocol.txt @@ -284,7 +284,9 @@ information is sent back to the client in the next step. The client can optionally request that pack-objects omit various objects from the packfile using one of several filtering techniques. These are intended for use with partial clone and partial fetch -operations. See `rev-list` for possible "filter-spec" values. +operations. An object that does not meet a filter-spec value is +omitted unless explicitly requested in a 'want' line. See `rev-list` +for possible filter-spec values. Once all the 'want's and 'shallow's (and optional 'deepen') are transferred, clients MUST send a flush-pkt, to tell the server side diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt index f58f24b1ef..09e4e0273f 100644 --- a/Documentation/technical/protocol-v2.txt +++ b/Documentation/technical/protocol-v2.txt @@ -298,12 +298,21 @@ included in the client's request: for use with partial clone and partial fetch operations. See `rev-list` for possible "filter-spec" values. +If the 'ref-in-want' feature is advertised, the following argument can +be included in the client's request as well as the potential addition of +the 'wanted-refs' section in the server's response as explained below. + + want-ref <ref> + Indicates to the server that the client wants to retrieve a + particular ref, where <ref> is the full name of a ref on the + server. + The response of `fetch` is broken into a number of sections separated by delimiter packets (0001), with each section beginning with its section header. output = *section - section = (acknowledgments | shallow-info | packfile) + section = (acknowledgments | shallow-info | wanted-refs | packfile) (flush-pkt | delim-pkt) acknowledgments = PKT-LINE("acknowledgments" LF) @@ -318,6 +327,10 @@ header. shallow = "shallow" SP obj-id unshallow = "unshallow" SP obj-id + wanted-refs = PKT-LINE("wanted-refs" LF) + *PKT-LINE(wanted-ref LF) + wanted-ref = obj-id SP refname + packfile = PKT-LINE("packfile" LF) *PKT-LINE(%x01-03 *%x00-ff) @@ -378,6 +391,19 @@ header. * This section is only included if a packfile section is also included in the response. + wanted-refs section + * This section is only included if the client has requested a + ref using a 'want-ref' line and if a packfile section is also + included in the response. + + * Always begins with the section header "wanted-refs". + + * The server will send a ref listing ("<oid> <refname>") for + each reference requested using 'want-ref' lines. + + * The server MUST NOT send any refs which were not requested + using 'want-ref' lines. + packfile section * This section is only included if the client has sent 'want' lines in its request and either requested that no more |