Hello @Junio, and thank you for feedback :)
If I understand correctly, you are suggesting that `git diff`/`git
apply` are behaving correctly here, but they might not be the right tool
for the job? I sort of sense that `git` could achieve this "z = x + 𝛥y"
folder operation (because it has all the machinery required to do so),
but I'm not sure how to leverage it correctly. Do I need to get into
"plumbing"?
--
Iago-lito
On 01/11/2024 08:05, Junio C Hamano wrote:
Iago-lito <iago-lito@xxxxxxx> writes:
Hello,
I have troubles understanding the behaviour of `git apply` with respect to renames in a `--no-index` context.
Let us craft a toy folder:
```sh
$ mkdir x
$ echo a > x/a # To be modified.
$ echo b > x/b # To be renamed.
```
Duplicate it twice to get three identical folders `x = y = z`.
```sh
$ cp -r x y
$ cp -r x z
```
Modify `y`:
```sh
$ echo newline >> y/a # Edit.
$ mv y/b y/c # Rename.
```
Now I would like to use git as a "better GNU patch".
Calculate the diff from `x` to `y`:
```sh
$ git diff --no-prefix x y | tee patch
diff --git x/a y/a
index 7898192..4030aa5 100644
--- x/a
+++ y/a
@@ -1 +1,2 @@
a
+newline
diff --git x/b y/c
similarity index 100%
rename from x/b
rename to y/c
```
Interesting. I think "git diff --no-index" is "wrong" here, but
"wrong" is not in the sense that it is _incorrect_, but in the sense
that it merely is incompatible with what you are trying to achieve.
If you had files a and b, modified a in place and renamed b to c,
and if you did this in a repository with tracked files, you would
have seen
$ git diff --src-prefix=x --dst-prefix=y
diff --git x/a y/a
index ...
--- x/a
+++ y/a
...
diff --git x/b y/c
similarity index 100%
rename from b
rename to c
Notice how "rename from" and "rename to" information is different in
the "real" git-diff output, as opposed to "git diff --no-index"
output you have?
At least when comparing two directories, "git diff --no-index X Y"
could be interpreted as a request to treat as if X and Y were
checkouts from two Git commits X and Y, and by comparing them the
output should be identical to the result of comparing the contents
of commits X and Y.
But feeding "git apply" however may not be the only reason why
people are using "diff --no-index X Y", and there may be a
legitimate reason why peole want to see "from x/b to y/c" in the
output, so unconditionally changing the output may very likely break
workflows of other people.
