| Junio C Hamano | 3dac504 | 2007-12-15 08:40:54 | [diff] [blame] | 1 | Def.: Shallow commits do have parents, but not in the shallow |
| 2 | repo, and therefore grafts are introduced pretending that |
| 3 | these commits have no parents. |
| 4 | |
| 5 | The basic idea is to write the SHA1s of shallow commits into |
| 6 | $GIT_DIR/shallow, and handle its contents like the contents |
| 7 | of $GIT_DIR/info/grafts (with the difference that shallow |
| 8 | cannot contain parent information). |
| 9 | |
| 10 | This information is stored in a new file instead of grafts, or |
| 11 | even the config, since the user should not touch that file |
| 12 | at all (even throughout development of the shallow clone, it |
| 13 | was never manually edited!). |
| 14 | |
| 15 | Each line contains exactly one SHA1. When read, a commit_graft |
| 16 | will be constructed, which has nr_parent < 0 to make it easier |
| 17 | to discern from user provided grafts. |
| 18 | |
| 19 | Since fsck-objects relies on the library to read the objects, |
| 20 | it honours shallow commits automatically. |
| 21 | |
| 22 | There are some unfinished ends of the whole shallow business: |
| 23 | |
| 24 | - maybe we have to force non-thin packs when fetching into a |
| 25 | shallow repo (ATM they are forced non-thin). |
| 26 | |
| 27 | - A special handling of a shallow upstream is needed. At some |
| 28 | stage, upload-pack has to check if it sends a shallow commit, |
| 29 | and it should send that information early (or fail, if the |
| 30 | client does not support shallow repositories). There is no |
| 31 | support at all for this in this patch series. |
| 32 | |
| 33 | - Instead of locking $GIT_DIR/shallow at the start, just |
| 34 | the timestamp of it is noted, and when it comes to writing it, |
| 35 | a check is performed if the mtime is still the same, dying if |
| 36 | it is not. |
| 37 | |
| 38 | - It is unclear how "push into/from a shallow repo" should behave. |
| 39 | |
| 40 | - If you deepen a history, you'd want to get the tags of the |
| 41 | newly stored (but older!) commits. This does not work right now. |
| 42 | |
| 43 | To make a shallow clone, you can call "git-clone --depth 20 repo". |
| 44 | The result contains only commit chains with a length of at most 20. |
| 45 | It also writes an appropriate $GIT_DIR/shallow. |
| 46 | |
| 47 | You can deepen a shallow repository with "git-fetch --depth 20 |
| 48 | repo branch", which will fetch branch from repo, but stop at depth |
| 49 | 20, updating $GIT_DIR/shallow. |
