[GSoC] Git Blog 3

[GSoC] Git Blog 3

[ZheNing Hu]

My third week blog finished:
The web version is here:
https://adlternative.github.io/GSOC-Git-Blog-3/

-----

## Week3: Meticulousness is very important

### What happened this week
- I found a `git cat-file` bug this week, see:

```bash
git cat-file --batch=batman --batch-all-objects
batman
fatal: object 00345b5fe0aa8f45e9d1289ceb299f0489ea3fe1 changed type!?
```

It seems that Git died for a strange reason: the type of
an object changed? Is my Git object damaged? (Just like
a friend of mine, use `find . -type f -print0 | xargs -0 sed
-i "s/\r//g"` remove all the '\r' of all files in a Git repository,
this caused most of his Git commands to fail.) So I tested
it under different linux platforms, they all have this same
damage.

After a series of testing and debugging, I found that
`oid_object_info_extended()` did not get the type of
object.

So I submitted the patch for fix this bug to the Git mailing list in
[[PATCH] [GSOC] cat-file: fix --batch report changed-type
bug](https://lore.kernel.org/git/pull.965.git.1622363366722.gitgitgadget@gmail.com/),
Peff tell us the essential reason for this bug:

In `845de33a5b (cat-file: avoid noop calls to
sha1_object_info_extended, 2016-05-18)`, this patches
skips the call to `oid_object_info_extended()` entirely when
`--batch-all-objects` is in use, and the custom format does
not include any placeholders that require calling it. The correct
solution is to put checking if `object_info` is empty after
setting `object_info.typep`.

Finally, thanks to the help of Jeff, I summit final patch in
[[PATCH v2 1/2] [GSOC] cat-file: handle trivial --batch format with
--batch-all-objects](https://lore.kernel.org/git/4af3b958dd056e2162fdc5d7f6600bcedde210b8.1622737766.git.gitgitgadget@gmail.com/).

Talk of experience as a story: Even experienced programmers
make small mistakes, writing any code requires very careful thinking.
- The checkpoints for rejecting `%(raw)` and `--<lang>` are incorrect.
At Junio’s reminder, I changed the checkpoint from
`parse_ref_filter_atom()` to `verify_ref_format()`. My mentor Christian
pointed out some grammatical errors in the cover letter.
- At the suggestion of Junio, I rebased `0efed94 ([GSOC]
ref-filter: add %(raw) atom)` on `1197f1a (ref-filter: introduce
enum atom_type)`, they have a clash, after resolving the conflict,
it's better for me to consider the code I implemented before and
the code I wrote now at the same time, I can find more problems
and find better solutions.
- I submitted the patch about `%(rest)`, `%(raw:textconv)` and
`%(raw:filters)` for `ref-filter`, they are used to simulate some
functions of `git cat-file`, my mentor Hariom noticed one of the
formatting issues, I am waiting for more reviews for the time being.

### What's the next step

As long as new atoms `%(rest)`, `%(raw:textconv)` and `%(raw:filters)`
for `ref-filter` can be accepted by Git, We can start to let `cat-file` use
`ref-filter` logic on a large scale! Exciting! But the performance of
`ref-filter`
is still not good. Perhaps I need to find a new breakthrough in the
performance bottleneck of `ref-filter`.

Thanks!
--
ZheNing Hu

Re: [GSoC] Git Blog 3

[Christian Couder]

On Sun, Jun 6, 2021 at 5:21 PM ZheNing Hu <adlternative@gmail.com> wrote:
>
> My third week blog finished:
> The web version is here:
> https://adlternative.github.io/GSOC-Git-Blog-3/

Thanks!

> -----
>
> ## Week3: Meticulousness is very important
>
> ### What happened this week
> - I found a `git cat-file` bug this week, see:
>
> ```bash
> git cat-file --batch=batman --batch-all-objects
> batman
> fatal: object 00345b5fe0aa8f45e9d1289ceb299f0489ea3fe1 changed type!?
> ```
>
> It seems that Git died for a strange reason: the type of
> an object changed? Is my Git object damaged? (Just like
> a friend of mine, use `find . -type f -print0 | xargs -0 sed

Maybe: s/, use/ used/
or: s/, use/, who used/

> -i "s/\r//g"` remove all the '\r' of all files in a Git repository,

s/remove/to remove/

> this caused most of his Git commands to fail.) So I tested
> it under different linux platforms, they all have this same

s/linux/Linux/

> damage.

Maybe: s/damage/breakage/

>
> After a series of testing and debugging, I found that
> `oid_object_info_extended()` did not get the type of
> object.
>
> So I submitted the patch for fix this bug to the Git mailing list in
> [[PATCH] [GSOC] cat-file: fix --batch report changed-type
> bug](https://lore.kernel.org/git/pull.965.git.1622363366722.gitgitgadget@gmail.com/),
> Peff tell us the essential reason for this bug:

Maybe: s/tell/told/

>
> In `845de33a5b (cat-file: avoid noop calls to
> sha1_object_info_extended, 2016-05-18)`, this patches

s/patches/patch/

> skips the call to `oid_object_info_extended()` entirely when
> `--batch-all-objects` is in use, and the custom format does
> not include any placeholders that require calling it. The correct
> solution is to put checking if `object_info` is empty after

s/put checking/check/

> setting `object_info.typep`.
>
> Finally, thanks to the help of Jeff, I summit final patch in

s/summit/submitted a/

> [[PATCH v2 1/2] [GSOC] cat-file: handle trivial --batch format with
> --batch-all-objects](https://lore.kernel.org/git/4af3b958dd056e2162fdc5d7f6600bcedde210b8.1622737766.git.gitgitgadget@gmail.com/).
>
> Talk of experience as a story: Even experienced programmers
> make small mistakes, writing any code requires very careful thinking.
> - The checkpoints for rejecting `%(raw)` and `--<lang>` are incorrect.
> At Junio’s reminder, I changed the checkpoint from
> `parse_ref_filter_atom()` to `verify_ref_format()`. My mentor Christian
> pointed out some grammatical errors in the cover letter.
> - At the suggestion of Junio, I rebased `0efed94 ([GSOC]
> ref-filter: add %(raw) atom)` on `1197f1a (ref-filter: introduce
> enum atom_type)`, they have a clash, after resolving the conflict,

Maybe: s/have/had/ and s/clash, after/clash. After/

or: s/they have a clash, after/they clashed. After/

> it's better for me to consider the code I implemented before and
> the code I wrote now at the same time, I can find more problems
> and find better solutions.
> - I submitted the patch about `%(rest)`, `%(raw:textconv)` and
> `%(raw:filters)` for `ref-filter`, they are used to simulate some

s/, they/. They/

> functions of `git cat-file`, my mentor Hariom noticed one of the

s/, my/. My/

> formatting issues, I am waiting for more reviews for the time being.
>
> ### What's the next step
>
> As long as new atoms `%(rest)`, `%(raw:textconv)` and `%(raw:filters)`

Maybe: s/long/soon/

> for `ref-filter` can be accepted by Git, We can start to let `cat-file` use

s/, We/, we/

> `ref-filter` logic on a large scale! Exciting! But the performance of
> `ref-filter`
> is still not good. Perhaps I need to find a new breakthrough in the
> performance bottleneck of `ref-filter`.

Great, thanks!

Re: [GSoC] Git Blog 3

[ZheNing Hu]

Christian Couder <christian.couder@gmail.com> 于2021年6月7日周一 下午12:45写道：
>
> On Sun, Jun 6, 2021 at 5:21 PM ZheNing Hu <adlternative@gmail.com> wrote:
> >
> > My third week blog finished:
> > The web version is here:
> > https://adlternative.github.io/GSOC-Git-Blog-3/
>
> Thanks!
>
> > -----
> >
> > ## Week3: Meticulousness is very important
> >
> > ### What happened this week
> > - I found a `git cat-file` bug this week, see:
> >
> > ```bash
> > git cat-file --batch=batman --batch-all-objects
> > batman
> > fatal: object 00345b5fe0aa8f45e9d1289ceb299f0489ea3fe1 changed type!?
> > ```
> >
> > It seems that Git died for a strange reason: the type of
> > an object changed? Is my Git object damaged? (Just like
> > a friend of mine, use `find . -type f -print0 | xargs -0 sed
>
> Maybe: s/, use/ used/
> or: s/, use/, who used/
>
> > -i "s/\r//g"` remove all the '\r' of all files in a Git repository,
>
> s/remove/to remove/
>
> > this caused most of his Git commands to fail.) So I tested
> > it under different linux platforms, they all have this same
>
> s/linux/Linux/
>
> > damage.
>
> Maybe: s/damage/breakage/
>
> >
> > After a series of testing and debugging, I found that
> > `oid_object_info_extended()` did not get the type of
> > object.
> >
> > So I submitted the patch for fix this bug to the Git mailing list in
> > [[PATCH] [GSOC] cat-file: fix --batch report changed-type
> > bug](https://lore.kernel.org/git/pull.965.git.1622363366722.gitgitgadget@gmail.com/),
> > Peff tell us the essential reason for this bug:
>
> Maybe: s/tell/told/
>
> >
> > In `845de33a5b (cat-file: avoid noop calls to
> > sha1_object_info_extended, 2016-05-18)`, this patches
>
> s/patches/patch/
>
> > skips the call to `oid_object_info_extended()` entirely when
> > `--batch-all-objects` is in use, and the custom format does
> > not include any placeholders that require calling it. The correct
> > solution is to put checking if `object_info` is empty after
>
> s/put checking/check/
>
> > setting `object_info.typep`.
> >
> > Finally, thanks to the help of Jeff, I summit final patch in
>
> s/summit/submitted a/
>
> > [[PATCH v2 1/2] [GSOC] cat-file: handle trivial --batch format with
> > --batch-all-objects](https://lore.kernel.org/git/4af3b958dd056e2162fdc5d7f6600bcedde210b8.1622737766.git.gitgitgadget@gmail.com/).
> >
> > Talk of experience as a story: Even experienced programmers
> > make small mistakes, writing any code requires very careful thinking.
> > - The checkpoints for rejecting `%(raw)` and `--<lang>` are incorrect.
> > At Junio’s reminder, I changed the checkpoint from
> > `parse_ref_filter_atom()` to `verify_ref_format()`. My mentor Christian
> > pointed out some grammatical errors in the cover letter.
> > - At the suggestion of Junio, I rebased `0efed94 ([GSOC]
> > ref-filter: add %(raw) atom)` on `1197f1a (ref-filter: introduce
> > enum atom_type)`, they have a clash, after resolving the conflict,
>
> Maybe: s/have/had/ and s/clash, after/clash. After/
>
> or: s/they have a clash, after/they clashed. After/
>
> > it's better for me to consider the code I implemented before and
> > the code I wrote now at the same time, I can find more problems
> > and find better solutions.
> > - I submitted the patch about `%(rest)`, `%(raw:textconv)` and
> > `%(raw:filters)` for `ref-filter`, they are used to simulate some
>
> s/, they/. They/
>
> > functions of `git cat-file`, my mentor Hariom noticed one of the
>
> s/, my/. My/
>
> > formatting issues, I am waiting for more reviews for the time being.
> >
> > ### What's the next step
> >
> > As long as new atoms `%(rest)`, `%(raw:textconv)` and `%(raw:filters)`
>
> Maybe: s/long/soon/
>
> > for `ref-filter` can be accepted by Git, We can start to let `cat-file` use
>
> s/, We/, we/
>
> > `ref-filter` logic on a large scale! Exciting! But the performance of
> > `ref-filter`
> > is still not good. Perhaps I need to find a new breakthrough in the
> > performance bottleneck of `ref-filter`.
>
> Great, thanks!

Well, there are many typos in this blog... I will correct them in time.

Thanks.
--
ZheNing Hu