let git-diff allow patch to delete empty files?

let git-diff allow patch to delete empty files?

[Sam Liddicott]

In some cases "patch" cannot apply diff's generated using git-diff, I've
had a "git diff" output look like this when an empty file was removed as
the only change:

diff --git a/source3/include/dcerpc.h b/source3/include/dcerpc.h
deleted file mode 100644
index e69de29..0000000

which patch rejected, saying:
patch: **** Only garbage was found in the patch input.

There is a ghastly diff notation recognized by patch, using the magic
date 1970-01-01 01:00:00.000000000 to signify deletion which git-diff
properly uses for non-empty files.

Empty files are a different matter because there is no unified diff that
can represent deletion of an empty file because patch doesn't like
unified diff's with no context.

However this equivalent pair works by making the file non-empty and then
deleting it.

diff -Nru 1/here 2/here
--- 1/here    2008-11-05 09:43:55.000000000 +0000
+++ 2/here    2008-11-05 09:43:58.000000000 +0000
@@ -0,0 +1 @@
+
diff -Nru 1/here 2/here
--- 1/here    2008-11-05 09:37:23.000000000 +0000
+++ 2/here    1970-01-01 01:00:00.000000000 +0100
@@ -1 +0,0 @@
-


In considering this filthy hack we should recognize that currently :

* patch will choke on certain "git diff" output. If patch's exit code is
checked as part of a loop of patches, then the patch procedure will
fail. This happened to me
* if delete-empty-file is one action in a larger patch file it will do
nothing - which can be worse if the "existence" of a file affects the
build system.

This filthy hack fixes both problems.

Sam

Re: let git-diff allow patch to delete empty files?

[Sam Liddicott]

[-- Attachment #1: Type: text/plain, Size: 804 bytes --]

* Sam Liddicott wrote, On 05/11/08 12:22:
> In some cases "patch" cannot apply diff's generated using git-diff, I've
> had a "git diff" output look like this when an empty file was removed as
> the only change:
>
> ..
> However this equivalent pair works by making the file non-empty and then
> deleting it.
>
> diff -Nru 1/here 2/here
> --- 1/here    2008-11-05 09:43:55.000000000 +0000
> +++ 2/here    2008-11-05 09:43:58.000000000 +0000
> @@ -0,0 +1 @@
> +
> diff -Nru 1/here 2/here
> --- 1/here    2008-11-05 09:37:23.000000000 +0000
> +++ 2/here    1970-01-01 01:00:00.000000000 +0100
> @@ -1 +0,0 @@
> -
>   
The same problem occurs with new empty files.

Attached is an awk filter which will expand out these git notes into the
2-part unified diff's.
It would be nicer if git did it natively.
Sam

[-- Attachment #2: git-new-delete-filter.awk --]
[-- Type: text/plain, Size: 1430 bytes --]

#! /usr/bin/awk -f

function do_empty() {
  if (diff!="" && deleted!="" && indx!="") {
    printf("Make patch give the file 1 line\n");
    printf("--- %s\n",diff);
    printf("+++ %s\n",diff);
    printf("@@ -0,0 +1 @@\n+\n");
    printf("Make patch delete the 1 line file\n");
    printf("--- %s\t\n",diff);
    printf("+++ /dev/null\t1970-01-01 01:00:00.000000000\n");
    printf("@@ -1 +0,0 @@\n-\n");
  }
  if (diff!="" && created!="" && indx!="") {
    printf("Make patch create the file with 1 line\n");
    printf("--- %s\n",diff);
    printf("+++ %s\n",diff);
    printf("@@ -0,0 +1 @@\n+\n");
    printf("Make patch create delete the line but keep the file\n");
    printf("--- %s\n",diff);
    printf("+++ %s\n",diff);
    printf("@@ -1 +0,0 @@\n-\n");
  }
  no_empty();
}

function no_empty() {
  diff="";
  deleted="";
  created="";
  indx="";
}

{
  if (in_hunk > 0) in_hunk--;
}

/^diff --git / {
  do_empty();
  if (! in_hunk) diff=$3;
}

/^deleted file mode / {
  if (! in_hunk && diff!="") deleted=$0;
}

/^new file mode / {
  if (! in_hunk && diff!="") created=$0;
}

/^index / {
  if (! in_hunk && diff!="") indx=$0;
}

/^--- / {
  no_empty();
}

/^@@ / {
  # read the hunk size
  p=index($2,",");
  if (p==0) c1=1;
  else c1=strtonum(substr($2, p+1));

  p=index($3,",");
  if (p==0) in_hunk=1;
  else in_hunk=strtonum(substr($2, p+1));

  if (c1 > in_hunk) in_hunk=c1;
}

{
  print;
}

END {
  do_empty();
}

Re: let git-diff allow patch to delete empty files?

[Nanako Shiraishi]

Quoting "Sam Liddicott" <sam@liddicott.com>:

> In some cases "patch" cannot apply diff's generated using git-diff, I've
> had a "git diff" output look like this when an empty file was removed as
> the only change:

Even if you do not use git to manage your changes, you can use "git apply" from outside of a git repository as a replacement for "patch".

-- 
Nanako Shiraishi
http://ivory.ap.teacup.com/nanako3/

Re: let git-diff allow patch to delete empty files?

[Sam Liddicott]

* Nanako Shiraishi wrote, On 05/11/08 21:09:
> Quoting "Sam Liddicott" <sam@liddicott.com>:
>
>   
>> In some cases "patch" cannot apply diff's generated using git-diff, I've
>> had a "git diff" output look like this when an empty file was removed as
>> the only change:
>>     
>
> Even if you do not use git to manage your changes, you can use "git apply" from outside of a git repository as a replacement for "patch".
>
>   
Good tip, thanks.

In this case it is rpmbuild that is doing the patching, and making git a
build-requires would not be popular.

Sam