error when git-diff get pipe args

chunguang qu· Nov 5, 2013, 00:03 UTC · lore

$ cat a 111 fdsf 333 $ cat b 111 222 333 $ git diff a b # OK

diff --git a/a b/b
index 768560b..641d574 100644
--- a/a
+++ b/b
@@ -1,3 +1,3 @@
 111
-fdsf
+222
 333
$ git diff <(cat a) <(cat b)          # ERROR: no result print out
diff --git a/dev/fd/63 b/dev/fd/62
index 311e262..554e9f4 120000
--- a/dev/fd/63
+++ b/dev/fd/62
@@ -1 +1 @@
-pipe:[729963]
\ No newline at end of file
+pipe:[729965]
\ No newline at end of file

# compare with diff
$ diff -u a b                            # OK
--- a 2013-11-05 00:18:17.394805923 +0800
+++ b 2013-11-05 00:18:25.546805865 +0800
@@ -1,3 +1,3 @@
 111
-fdsf
+222
 333
$ diff -u <(cat a) <(cat b)         # OK: get result in same case
--- /dev/fd/63 2013-11-05 01:02:59.706787117 +0800
+++ /dev/fd/62 2013-11-05 01:02:59.706787117 +0800
@@ -1,3 +1,3 @@
 111
-fdsf
+222
 333

brian m. carlson· Nov 5, 2013, 00:08 UTC · re: chunguang qu · lore

Re: error when git-diff get pipe args

On Tue, Nov 05, 2013 at 08:03:28AM +0800, chunguang qu wrote:

Show 28 quoted lines

> $ cat a
> 111
> fdsf
> 333
> $ cat b
> 111
> 222
> 333
> $ git diff a b                             # OK
> diff --git a/a b/b
> index 768560b..641d574 100644
> --- a/a
> +++ b/b
> @@ -1,3 +1,3 @@
>  111
> -fdsf
> +222
>  333
> $ git diff <(cat a) <(cat b)          # ERROR: no result print out
> diff --git a/dev/fd/63 b/dev/fd/62
> index 311e262..554e9f4 120000
> --- a/dev/fd/63
> +++ b/dev/fd/62
> @@ -1 +1 @@
> -pipe:[729963]
> \ No newline at end of file
> +pipe:[729965]
> \ No newline at end of file

This is because git diff compares symlinks instead of dereferencing them, as diff does. On Linux, /dev/fd is a symlink to /proc/self/fd, and the items in that directory are all symlinks.

git diff is not generally intended to diff arbitrary files from arbitrary locations. For that, you want plain old diff, which works as you expect.

-- 
brian m. carlson / brian with sandals: Houston, Texas, US
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