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Does Git now have any C struct version history tracking mechanism?

Subject: Does Git now have any C struct version history tracking mechanism?

## tl;dr

4 messages between Aug 18, 2013 and Aug 20, 2013.

replies: 3people: 3as markdown or json

Zhan Jianyu· Aug 18, 2013, 10:33 UTC · lore
Hi, all.
* Background
  Such a requirement came into my mind when I am tracking a gloomy C
struct , with lengthy list of elements which are either elaborated or
opaque. So I use git blame to track it down and found that its
original version is quite simple and intuitive. So I think I could
just slice out every snapshot of this struct, reading every changelog
, to get a better knowledge of what it is and why it should be like
this.

It seems quite helpful but the process is quite cumbersome. So I wonder if there is already some mechanism fulfilling my requirement in Git. If it doesn't, would it be worthy adding one ?

Thanks
--

Regards, Zhan Jianyu

Nazri Ramliy· Aug 19, 2013, 05:54 UTC · re: Zhan Jianyu · lore

Re: Does Git now have any C struct version history tracking mechanism?

On Sun, Aug 18, 2013 at 6:33 PM, Zhan Jianyu <nasa4836@gmail.com> wrote:
Show 11 quoted lines
>   Such a requirement came into my mind when I am tracking a gloomy C
> struct , with lengthy list of elements which are either elaborated or
> opaque. So I use git blame to track it down and found that its
> original version is quite simple and intuitive. So I think I could
> just slice out every snapshot of this struct, reading every changelog
> , to get a better knowledge of what it is and why it should be like
> this.
>
> It seems quite helpful but the process is quite cumbersome. So I
> wonder if there is already some mechanism fulfilling my requirement in
> Git.  If it doesn't,  would it be worthy adding one ?

It's already merged to git.git's master quite recently in ed73fe56428eecd2b635473f6a517a183c4713a3 (back in June).

You'd invoke git log like this:
    $ git log -L :struct_or_function_name:filename.c

and it will show you the commits and the specific hunks that affect the struct or function name.

It's still a bit rough on the edges, for example, doing the following in git.git:

    $ git log -L :rev_cmdline_info:revision.h

Shows three commits (a765499, ca92e59 and 281eee4) where the second one does not touch the struct at all (if you do "git show ca92e59" you might gain an insight as to how -L works).

But that is not to say that it's not good. The gain really shadows the roughness.

nazri
Thomas Rast· Aug 19, 2013, 08:37 UTC · re: Nazri Ramliy · lore

Re: Does Git now have any C struct version history tracking mechanism?

Nazri Ramliy <ayiehere@gmail.com> writes:
Show 31 quoted lines
> On Sun, Aug 18, 2013 at 6:33 PM, Zhan Jianyu <nasa4836@gmail.com> wrote:
>>   Such a requirement came into my mind when I am tracking a gloomy C
>> struct , with lengthy list of elements which are either elaborated or
>> opaque. So I use git blame to track it down and found that its
>> original version is quite simple and intuitive. So I think I could
>> just slice out every snapshot of this struct, reading every changelog
>> , to get a better knowledge of what it is and why it should be like
>> this.
>>
>> It seems quite helpful but the process is quite cumbersome. So I
>> wonder if there is already some mechanism fulfilling my requirement in
>> Git.  If it doesn't,  would it be worthy adding one ?
>
> It's already merged to git.git's master quite recently in
> ed73fe56428eecd2b635473f6a517a183c4713a3 (back in June).
>
> You'd invoke git log like this:
>
>     $ git log -L :struct_or_function_name:filename.c
>
> and it will show you the commits and the specific hunks that affect
> the struct or function name.
>
> It's still a bit rough on the edges, for example, doing the following
> in git.git:
>
>     $ git log -L :rev_cmdline_info:revision.h
>
> Shows three commits (a765499, ca92e59 and 281eee4) where the second
> one does not touch the struct at all (if you do "git show ca92e59" you
> might gain an insight as to how -L works).

Hmm, IIUC that's actually not a bug or even a roughness; it's an artifact of how the :pattern:file syntax is defined. It takes the first _funcname line_ matching 'pattern', up to (but excluding) the next funcname line.

The default funcname rule (in the absence of any patterns) does not match '#define...' on account of the '#'. The default funcname pattern for 'cpp' (if you manually configured your git.git repo to set this attribute; it doesn't by default) never matches a leading '#´ either. So it's no surprise that the tracked range extends a few more lines after the struct.

Or is there an issue that I'm missing?
-- 
Thomas Rast
trast@{inf,student}.ethz.ch
Nazri Ramliy· Aug 20, 2013, 03:55 UTC · re: Thomas Rast · lore

Re: Does Git now have any C struct version history tracking mechanism?

On Mon, Aug 19, 2013 at 4:37 PM, Thomas Rast <trast@inf.ethz.ch> wrote:
Show 5 quoted lines
> Hmm, IIUC that's actually not a bug or even a roughness; it's an
> artifact of how the :pattern:file syntax is defined.  It takes the first
> _funcname line_ matching 'pattern', up to (but excluding) the next
> funcname line.
>
...
> Or is there an issue that I'm missing?
No you're correct. I should have used the following instead for the demo:
    $ git log -L /struct\ rev_cmdline_info/,/^}/:revision.h
Moral: You'd hit your target better if you work on your aim.
nazri

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