Hello, Git, I'm ZheNing Hu, Here is my GSoC 2021 Proposal draft. And website version is there : https://docs.google.com/document/d/119k-Xa4CKOt5rC1gg1cqPr6H3MvdgTUizndJGAo1Erk/edit Welcome any Comments and Correct :) ----8<---- ## Use ref-filter formats in git cat-file ### About Me | Name | ZheNing Hu | | ---------- | ------------------------------------------ | | Major | Computer Science And Technology | | Mobile no. | +86 15058356458 | | Email | adlternative@xxxxxxxxx | | IRC | adlternative (on #git-devel/#git@freenode) | | Github | https://github.com/adlternative/ | | Blogs | https://adlternative.github.io/ | | Time Zone | CST (UTC +08:00) | ### Education & Background * I am currently a 2nd Year Student majoring in computer science and technology in Xi'an University of Posts & Telecommunications (China). * In my freshman year, I joined the XiYou Linux Group of the university and learned how to use Git to submit my own code to GitHub. I have learned C, C++, Python and shell in two years, I know how to use gdb debugging, and I am familiar with relevant knowledge of Linux System Programming and Linux Network Programming. * I started learning Git source code and made contributions to Git from December of 2020. ### Me & Git Around last November, I found a couple of projects [build-your-own-git](https://github.com/danistefanovic/build-your-own-x#build-your-own-git) on GitHub teaching me how to write a simple git, the mechanics of Git are very interesting: 1. There are four types of objects in Git: BLOB, TREE, COMMIT, TAG 2. The (loose)objects are stored in `.git/object/sha1[0-1]/sha1[2-39]` with the sha1 value of the data as the storage address. 3. All branches are just references to commits. Then I read`《Pro Git》`and Jiang Xin's `《Git Authoritative Guide》`, learned the use of most Git subcommands. Later, I started learning some of the Git source code, I found Git has at least 200,000 lines of C code and 200,000 lines of shell script code, which leaves me a little confused about where to start. But then, after I submitted my first patch, a lot of people in the Git community came over and gave me very enthusiastic guidance, which gave me the courage to learn the Git source code, and then I started making my own contributions, You can find them here: [gitgitgadget](https://github.com/gitgitgadget/git/pulls?q=is%3Apr+author%3Aadlternative+) or [git.kernel.org](https://git.kernel.org/pub/scm/git/git.git/log/?qt=grep&q=ZheNing+Hu) These patches have been merged into the "master" branch: #### [master] * difftool.c: learn a new way start at specified file [(mail list)](https://lore.kernel.org/git/pull.870.v6.git.1613739235241.gitgitgadget@xxxxxxxxx/) * ls-files.c: add --deduplicate option [(mail list)](https://lore.kernel.org/git/384f77a4c188456854bd86335e9bdc8018097a5f.1611485667.git.gitgitgadget@xxxxxxxxx/) * ls_files.c: consolidate two for loops into one [(mail list)](https://lore.kernel.org/git/f9d5e44d2c08b9e3d05a73b0a6e520ef7bb889c9.1611485667.git.gitgitgadget@xxxxxxxxx/) * ls_files.c: bugfix for --deleted and --modified [(mail list)](https://lore.kernel.org/git/8b02367a359e62d7721b9078ac8393a467d83724.1611485667.git.gitgitgadget@xxxxxxxxx/) * builtin/*: update usage format [(mail list)](https://lore.kernel.org/git/d3eb6dcff1468645560c16e1d8753002cbd7f143.1609944243.git.gitgitgadget@xxxxxxxxx/) And These patches are in the queue: #### [next] * format-patch: allow a non-integral version numbers [(mail list)](https://lore.kernel.org/git/pull.885.v10.git.1616497946427.gitgitgadget@xxxxxxxxx/) * [GSOC] commit: add --trailer option [(mail list)](https://lore.kernel.org/git/pull.901.v14.git.1616507757999.gitgitgadget@xxxxxxxxx/) #### [WIP] * gitk: add right-click context menu for tags [(mail list)](https://lore.kernel.org/git/pull.866.v5.git.1614227923637.gitgitgadget@xxxxxxxxx/) * [GSOC] trailer: pass arg as positional parameter [(mail list)](https://lore.kernel.org/git/5894d8c4b36466326b0427bfda0d6981e52a0907.1617185147.git.gitgitgadget@xxxxxxxxx/) ### Proposed Project * Git used to have an old problem of duplicated implementations of some logic. For example, Git had at least 4 different implementations to format command output for different commands. * `git cat-file` is a git subcommand used to see information about a git object. * `git cat-file --batch` can print object information and contents on stdin. The only difference between `--batch-check` and `--batch` is that `--batch-check` does not print the contents of the object. * `--batch-all-objects` will show all objects with `--batch` or `--batch-check`. * `--batch-check` and `--batch` both accept formatted strings: * `%(objectname)`: 40-bit SHA1 string of Git object * `%(objecttype)`: Object Type blob,tree,commit,tag * `%(objectsize)`: Size of the object's content * `%(objectsize:disk)`: The size of the object itself on disk * `%(delatbase)`: If the object is stored incrementally in Git, Returns the SHA1 string for its delabase * `%(rest)`: Anything before the space and TAB in the input line is treated as an object, and anything after that will be printed as usual * In the original design, the first time use `expand_format()` in `batch_objects()` is to parsing formatted messages, the second time use `expand_format()` in `batch_object_write()` is to format the object information and store it in a string buffer, eventually the contents of this buffer will be printed to standard output. * [Olga](olyatelezhnaya@xxxxxxxxx) have been involved in integrating `ref-filter` logic into `cat-file` [(link)](https://github.com/git/git/pull/568), the problem with her patches at that time: 1. Too long patch series, difficult to adjust and merge. 2. I don't think it's a good idea for her to use `struct ref_array_item` instead of `struct expand_data` for `cat-file` to fit `ref-filter` logic, because `struct ref_array_item` and `struct expand_data` are not very related. [(link)](https://github.com/git/git/pull/568/commits/e0aafaa76476ba5528f84b794043531ebd4633c7#diff-d03110606a7ed8cb9832bbcc572f1093435cc6115c4e58d7a7750af3c33319a7R238) * Because part of the feature of `git for-each-ref` is very similar to that of `git cat-file`, I think `git cat-file` can learn some feasible solutions from it. #### My possible solutions: 1. Same [solution](https://github.com/git/git/pull/568/commits/cc40c464e813fc7a6bd93a01661646114d694d76) as Olga, add member `struct ref_format format` in `struct batch_options`. 2. Use the function [`verify_ref_format()`](https://github.com/gitgitgadget/git/blob/84d06cdc06389ae7c462434cb7b1db0980f63860/ref-filter.c#L904) to replace the first `expand_format()` for parsing format strings. 3. Write a function like [`format_ref_array_item()`](https://github.com/gitgitgadget/git/blob/84d06cdc06389ae7c462434cb7b1db0980f63860/ref-filter.c#L2392), get information about objects, and use `get_object()` to grub the information which we prefer (or just use `grab_common_value()`). 4. The migration of `%(rest)` may require learning the handling of `%(if)` ,`%(else)`. ### Are you applying for other Projects? No, Git is the only one. ### Blogging about Git In fact, while I am studying Git source code, I often write some [blogs](https://adlternative.github.io/tags/git/) to record my learning content, this helps me to recall some content after forgetting it. Most of the blogs were written in Chinese previously, but during the GSoC, I promise all my blogs will be written in English. ### TimeLine * May 18 ~ June 8 * Look for a scheme to make `git cat-file` and `ref-filter` more compatible, and start the integration attempt. * *Stretch Goal*: move `%(objectsize)`,`%(objecttype)`,`%(objectname)` . * June 8 ~ July 8 * Move the body of the `git cat-file` attempt to the `ref-filter` logic, complete the basic function realization. * *Stretch Goal*: move `%(deltabase)`,`%(objectsize:disk)`,`%(rest)` . * July 8 ~ August 17 * Analyze the performance of ref-filter and try to reduce the performance cost of a lot of string matching. I thought if I had some spare time, I could work on some other interesting patches. * *Stretch Goal*: Optimize ref-filter performance. ### Availability My exam is expected to end in June, but the time I don't have classes before the final exam, as well as the summer vacation after that, is basically my self-learning time. Although I am studying many other courses, I have enough time and energy to complete daily tasks. I'm staying active on the Git mailing list, you can find me at any time as long as I am not sleeping. :) ### Post GSoC * I love open source philosophy, willing to spread the spirit of openness, freedom and willing to research technology with like-minded people. * In my previous contact with the Git community in the past few months, many people in the Git community gave me great encouragement. I hope I can keep my passion for Git alive, contribute my own code, and pass this cool thing on. * I am willing to contribute code to the Git community for a long time after the end of GSoC. * I hope the Git community can give me a chance to participate in GSoC. I sincerely thank GSoC and the Git community!
