From: Dyrone Teng <dyroneteng@xxxxxxxxx> Partial clones are created using 'git clone', but there is no related help information in the git-clone documentation. Add a relevant section to help users understand what partial clones are and how they differ from normal clones. The section briefly introduces the applicable scenarios and some precautions of partial clone. If users want to know more about its technical design and other details, users can view the link of git-partial-clone(7) according to the guidelines in the section. Signed-off-by: Dyrone Teng <dyroneteng@xxxxxxxxx> --- Documentation/git-clone.txt | 72 +++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt index eafa1c39927..a6e13666ea1 100644 --- a/Documentation/git-clone.txt +++ b/Documentation/git-clone.txt @@ -310,6 +310,78 @@ or `--mirror` is given) for `host.xz:foo/.git`). Cloning into an existing directory is only allowed if the directory is empty. +Partial Clone +------------- + +By default, `git clone` will download every reachable object, including +every version of every file in the history of the repository. The +**partial clone** feature allows Git to transfer fewer objects and +request them from the remote only when they are needed, so some +reachable objects can be omitted from the initial `git clone` and +subsequent `git fetch` operations. + +To use the partial clone feature, you can run `git clone` with the +`--filter=<filter-spec>` option. If you want to clone a repository +without download any blobs, the form `filter=blob:none` will omit all +the blobs. If the repository has some large blobs and you want to +prevent some large blobs being downloaded by an appropriate threshold, +the form `--filter=blob:limit=<n>[kmg]`omits blobs larger than n bytes +or units (see linkgit:git-rev-list[1]). + +As mentioned before, a partially cloned repository may have to request +the missing objects when they are needed. So some 'local' commands may +fail without a network connection to the remote repository. + +For example, The <repository> contains two branches which names 'master' +and 'topic. Then, we clone the repository by + + $ git clone --filter=blob:none --no-checkout <repository> + +With the `--filter=blob:none` option Git will omit all the blobs and +the `--no-checkout` option Git will not perform a checkout of HEAD +after the clone is complete. Then, we check out the remote tracking +'topic' branch by + + $ git checkout -b topic origin/topic + +The output looks like + +------------ + remote: Enumerating objects: 1, done. + remote: Counting objects: 100% (1/1), done. + remote: Total 1 (delta 0), reused 0 (delta 0), pack-reused 0 + Receiving objects: 100% (1/1), 43 bytes | 43.00 KiB/s, done. + Branch 'topic' set up to track remote branch 'topic' from 'origin'. + Switched to a new branch 'topic' +------------ + +The output is a bit surprising but it shows how partial clone works. +When we check out the branch 'topic' Git will request the missing blobs +because they are needed. Then, We can switch back to branch 'master' by + + $ git checkout master + +This time the output looks like + +------------ + Switched to branch 'master' + Your branch is up to date with 'origin/master'. +------------ + +It shows that when we switch back to the previous location, the checkout +is done without a download because the repository has all the blobs that +were downloaded previously. + +`git log` may also make a surprise with partial clones. `git log +-- <pathspec>` will not cause downloads with the blob filters, because +it's only reading commits and trees. In addition to any options that +require git to look at the contents of blobs, like "-p" and "--stat" +, options that cause git to report pathnames, like "--summary" and +"--raw", will trigger lazy/on-demand fetching of blobs, as they are +needed to detect inexact renames. + +linkgit:partial-clone[1] + :git-clone: 1 include::urls.txt[] -- gitgitgadget
