Re: [PATCH v3] reset: add an example of how to split a commit into two

[Jacob Keller]

On Thu, Feb 16, 2017 at 11:49 AM, Junio C Hamano  wrote:
> Junio C Hamano  writes:
>
>> Jacob Keller  writes:
>>
>>> The interdiff between v2 and v3 is not really worth showing since I
>>> basically re-wrote the entire section a bit.
>>
>> Could this be made into an incremental, now that v2 has been in
>> 'next' for about 10 days, please?
>
> Nah, I think it is easier to read "log -p" if I just revert v2 out
> of existence from 'next', and queue this (with a minor typofixes) as
> a different topic to be merged later to 'master'.
>

Ok. Yea, I didn't even realize it was put into next because of the
various comments I'd received. I guess I could have checked, but the
diff really is bad when seeing incrementally.

> So no need to resend and certainly no need to make it incremental.
>
>>> +Split a commit apart into a sequence of commits::
>>> ++
>>> +Suppose that you have create lots of logically separate changes and commit 
>>> them
>>
>> s/create//; s/commit//
>
> I'd do this myself while queuing.
>
> Thanks.

Thanks,
Jake

Re: [PATCH v3] reset: add an example of how to split a commit into two

[Junio C Hamano]

Junio C Hamano  writes:

> Jacob Keller  writes:
>
>> The interdiff between v2 and v3 is not really worth showing since I
>> basically re-wrote the entire section a bit.
>
> Could this be made into an incremental, now that v2 has been in
> 'next' for about 10 days, please?

Nah, I think it is easier to read "log -p" if I just revert v2 out
of existence from 'next', and queue this (with a minor typofixes) as
a different topic to be merged later to 'master'.

So no need to resend and certainly no need to make it incremental.

>> +Split a commit apart into a sequence of commits::
>> ++
>> +Suppose that you have create lots of logically separate changes and commit 
>> them
>
> s/create//; s/commit//

I'd do this myself while queuing.

Thanks.

>
>> +together. Then, later you decide that it might be better to have each 
>> logical
>> +chunk associated with its own commit. ...

Re: [PATCH v3] reset: add an example of how to split a commit into two

[Junio C Hamano]

Jacob Keller  writes:

> The interdiff between v2 and v3 is not really worth showing since I
> basically re-wrote the entire section a bit.

Could this be made into an incremental, now that v2 has been in
'next' for about 10 days, please?

> +Split a commit apart into a sequence of commits::
> ++
> +Suppose that you have create lots of logically separate changes and commit 
> them

s/create//; s/commit//

> +together. Then, later you decide that it might be better to have each logical
> +chunk associated with its own commit. You can use git reset to rewind history
> +without changing the contents of your local files, and then successively use
> +git add -p to interactively select which hunks to include into each commit,
> +using git commit -c to pre-populate the commit message.
> ++
> +
> +$ git reset -N HEAD^<1>
> +$ git add -p<2>
> +$ git diff --cached <3>
> +$ git commit -c HEAD@{1}<4>
> +... <5>
> +$ git add ...   <6>
> +$ git diff --cached <7>
> +$ git commit ...<8>
> +
> ++
> +<1> First, reset the history back one commit so that we remove the original
> +commit, but leave the working tree with all the changes. The -N ensures
> +that any new files added with HEAD are still marked so that git add -p
> +will find them.
> +<2> Next, we interactively select diff hunks to add using the git add -p
> +facility. This will ask you about each diff hunk in sequence and you can
> +use simple commands such as "yes, include this", "No don't include this"
> +or even the very powerful "edit" facility.
> +<3> Once satisfied with the hunks you want to include, you should verify what
> +has been prepared for the first commit by using git diff --cached. This
> +shows all the changes that have been moved into the index and are about
> +to be committed.
> +<4> Next, commit the changes stored in the index. The -c option specifies to
> +pre-populate the commit message from the original message that you 
> started
> +with in the first commit. This is helpful to avoid retyping it. The 
> HEAD@{1}
> +is a special notation for the commit that HEAD used to be at prior to the
> +original reset commit (1 change ago). See linkgit:git-reflog[1] for more
> +details. You may also use any other valid commit reference.
> +<5> You can repeat steps 2-4 multiple times to break the original code into
> +any number of commits.
> +<6> Now you've split out many of the changes into their own commits, and 
> might
> +no longer use the patch mode of git add, in order to select all remaining
> +uncommitted changes.
> +<7> Once again, check to verify that you've included what you want to. You 
> may
> +also wish to verify that git diff doesn't show any remaining changes to 
> be
> +committed later.
> +<8> And finally create the final commit.
> +

Nicely done.  We could talk more "best practice" things in this
sequence (e.g. "'stash --keep' then test in isolation"), but it is
already sufficiently long, so extending it may hurt the readability
more than it helps by guiding the readers to better ways.

[PATCH v3] reset: add an example of how to split a commit into two

[Jacob Keller]

From: Jacob Keller 

It is often useful to break a commit into multiple parts that are more
logical separations. This can be tricky to learn how to do without the
brute-force method if re-writing code or commit messages from scratch.

Add a section to the git-reset documentation which shows an example
process for how to use git add -p and git commit -c HEAD@{1} to
interactively break a commit apart and re-use the original commit
message as a starting point when making the new commit message.

Signed-off-by: Jacob Keller 
Signed-off-by: Junio C Hamano 
---
The interdiff between v2 and v3 is not really worth showing since I
basically re-wrote the entire section a bit. I reworded the descriptions
and steps to indicate that you can break a commit apart into an
arbitrary number of separate commits. I also added a bit more
explanation to each step, and separately numbered the "repeat some steps
multiple times" portion.

 Documentation/git-reset.txt | 48 +
 1 file changed, 48 insertions(+)

diff --git a/Documentation/git-reset.txt b/Documentation/git-reset.txt
index 25432d9257f9..67a63574092d 100644
--- a/Documentation/git-reset.txt
+++ b/Documentation/git-reset.txt
@@ -292,6 +292,54 @@ $ git reset --keep start<3>
 <3> But you can use "reset --keep" to remove the unwanted commit after
 you switched to "branch2".
 
+Split a commit apart into a sequence of commits::
++
+Suppose that you have create lots of logically separate changes and commit them
+together. Then, later you decide that it might be better to have each logical
+chunk associated with its own commit. You can use git reset to rewind history
+without changing the contents of your local files, and then successively use
+git add -p to interactively select which hunks to include into each commit,
+using git commit -c to pre-populate the commit message.
++
+
+$ git reset -N HEAD^<1>
+$ git add -p<2>
+$ git diff --cached <3>
+$ git commit -c HEAD@{1}<4>
+... <5>
+$ git add ...   <6>
+$ git diff --cached <7>
+$ git commit ...<8>
+
++
+<1> First, reset the history back one commit so that we remove the original
+commit, but leave the working tree with all the changes. The -N ensures
+that any new files added with HEAD are still marked so that git add -p
+will find them.
+<2> Next, we interactively select diff hunks to add using the git add -p
+facility. This will ask you about each diff hunk in sequence and you can
+use simple commands such as "yes, include this", "No don't include this"
+or even the very powerful "edit" facility.
+<3> Once satisfied with the hunks you want to include, you should verify what
+has been prepared for the first commit by using git diff --cached. This
+shows all the changes that have been moved into the index and are about
+to be committed.
+<4> Next, commit the changes stored in the index. The -c option specifies to
+pre-populate the commit message from the original message that you started
+with in the first commit. This is helpful to avoid retyping it. The 
HEAD@{1}
+is a special notation for the commit that HEAD used to be at prior to the
+original reset commit (1 change ago). See linkgit:git-reflog[1] for more
+details. You may also use any other valid commit reference.
+<5> You can repeat steps 2-4 multiple times to break the original code into
+any number of commits.
+<6> Now you've split out many of the changes into their own commits, and might
+no longer use the patch mode of git add, in order to select all remaining
+uncommitted changes.
+<7> Once again, check to verify that you've included what you want to. You may
+also wish to verify that git diff doesn't show any remaining changes to be
+committed later.
+<8> And finally create the final commit.
+
 
 DISCUSSION
 --
-- 
2.12.0.rc0.177.g63172abf21d0