From c8bae7493d2f2910b57f13ded012e86bdcfb0532 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 16:47:53 +0200 Subject: Adding upstream version 1:2.39.2. Signed-off-by: Daniel Baumann --- Documentation/technical/shallow.txt | 60 +++++++++++++++++++++++++++++++++++++ 1 file changed, 60 insertions(+) create mode 100644 Documentation/technical/shallow.txt (limited to 'Documentation/technical/shallow.txt') diff --git a/Documentation/technical/shallow.txt b/Documentation/technical/shallow.txt new file mode 100644 index 0000000..f3738ba --- /dev/null +++ b/Documentation/technical/shallow.txt @@ -0,0 +1,60 @@ +Shallow commits +=============== + +.Definition +********************************************************* +Shallow commits do have parents, but not in the shallow +repo, and therefore grafts are introduced pretending that +these commits have no parents. +********************************************************* + +$GIT_DIR/shallow lists commit object names and tells Git to +pretend as if they are root commits (e.g. "git log" traversal +stops after showing them; "git fsck" does not complain saying +the commits listed on their "parent" lines do not exist). + +Each line contains exactly one object name. When read, a commit_graft +will be constructed, which has nr_parent < 0 to make it easier +to discern from user provided grafts. + +Note that the shallow feature could not be changed easily to +use replace refs: a commit containing a `mergetag` is not allowed +to be replaced, not even by a root commit. Such a commit can be +made shallow, though. Also, having a `shallow` file explicitly +listing all the commits made shallow makes it a *lot* easier to +do shallow-specific things such as to deepen the history. + +Since fsck-objects relies on the library to read the objects, +it honours shallow commits automatically. + +There are some unfinished ends of the whole shallow business: + +- maybe we have to force non-thin packs when fetching into a + shallow repo (ATM they are forced non-thin). + +- A special handling of a shallow upstream is needed. At some + stage, upload-pack has to check if it sends a shallow commit, + and it should send that information early (or fail, if the + client does not support shallow repositories). There is no + support at all for this in this patch series. + +- Instead of locking $GIT_DIR/shallow at the start, just + the timestamp of it is noted, and when it comes to writing it, + a check is performed if the mtime is still the same, dying if + it is not. + +- It is unclear how "push into/from a shallow repo" should behave. + +- If you deepen a history, you'd want to get the tags of the + newly stored (but older!) commits. This does not work right now. + +To make a shallow clone, you can call "git-clone --depth 20 repo". +The result contains only commit chains with a length of at most 20. +It also writes an appropriate $GIT_DIR/shallow. + +You can deepen a shallow repository with "git-fetch --depth 20 +repo branch", which will fetch branch from repo, but stop at depth +20, updating $GIT_DIR/shallow. + +The special depth 2147483647 (or 0x7fffffff, the largest positive +number a signed 32-bit integer can contain) means infinite depth. -- cgit v1.2.3