Re: [RFC/PATCH 2/1] fixup! Documentation: start to explain what git replace is for

[Maaartin-1 <grajcar1@seznam.cz>]

On 11-01-14 09:49, Jonathan Nieder wrote:
> Some tweaks suggested by Maaartin:

[snip]

> [side note: please do not prune the cc list; I only stumbled on this
> message in the online archive by luck]

What could I have done about it? I didn't received it by email and
answered using post.gmane.org. There's no way to add CC there. If I'd
wrote an email instead, it wouldn't be placed in the thread.

[snip]

>>> +<1> Find all parentless commits in the 'master' branch;
>>> +for 'master' read the branch holding v2.5 history.
>>
>> Aren't you later calling it "FIRST" and assuming there's only one?
> 
> Hmm.  I want to say that there _could_ be multiple parentless commits
> in the v2.5 history and we are treating one of them as its root (just
> like git master has multiple parentless ancestors but e83c5163 is
> conventionally considered its beginning).  Not sure how to write that
> clearly.

Maybe just something like "Let's assume there's only one and let's call
it FIRST". For the example, this is enough.

>> Isn't the combination of "-i" (=in-place edit) with redirection wrong?
> 
> Good catch (the "-i" is a typo).

I'd go the other way round and use "-i" so I'd need only one file. Using
a shell variable instead would be even better, s. below.

[snip]

I tried to use the vars instead of files below, but never tested it. I
used "first_commit" instead of both "tmp" and "new", which is not really
nice.

> +$ git rev-list master --parents | grep -v ' '
> +$ first=$(git rev-list master --parents | grep -v ' ') <1>
> +$ git rev-parse v2.4                                   <2>
> +$ git cat-file commit $first >tmp                      <3>

$ first_commit = $(git cat-file commit FIRST)       <3>

> +$ sed "/^tree / a \\
> +parent $(git rev-parse v2.4)" <tmp >new                <4>

$ first_commit = $($ echo $first_commit |
sed  "/^tree / a \\
parent $(git rev-parse v2.4)")                      <4>

Unfortunately, the line got too long. For sed unaware people like me it
may not be obvious that a line break is required. I'd use perl, anyway.

$ first_commit = $($ echo $first_commit |
perl -p
"s/^tree .*/$&\nparent $(git rev-parse v2.4)/")      <4>

> +$ new_commit=$(git hash-object -t commit -w new)       <5>

$ new_commit=$(echo $first_commit |
git hash-object -t commit -w --stdin)       <5>

[snip]