Re: [PATCH v3 2/2] diff: index-line: respect --abbrev in object's name

> A handful of Git's commands respect `--abbrev' for customizing length
> of abbreviation of object names.
> 
> For diff-family, Git supports 2 different options for 2 different
> purposes, `--full-index' for showing diff-patch object's name in full,
> and `--abbrev' to customize the length of object names in diff-raw and
> diff-tree header lines, without any options to customise the length of
> object names in diff-patch format. When working with diff-patch format,
> we only have two options, either full index, or default abbrev length.
> 
> Although, that consistent is documented, it doesn't stop users from
> trying to use `--abbrev' with the hope of customising diff-patch's
> objects' name's abbreviation.
> 
> Let's resolve that inconsistency.
> 
> To preserve backward compatibility with old script that specify both
> `--full-index' and `--abbrev', always shows full object id
> if `--full-index' is specified.
> 
> Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
> ---
>  Documentation/diff-options.txt                |  9 +++---
>  diff.c                                        |  5 +++-
>  t/t4013-diff-various.sh                       |  3 ++
>  ...ff.diff-tree_--root_-p_--abbrev=10_initial | 29 +++++++++++++++++++
>  ...--root_-p_--full-index_--abbrev=10_initial | 29 +++++++++++++++++++
>  ...f.diff-tree_--root_-p_--full-index_initial | 29 +++++++++++++++++++
>  6 files changed, 99 insertions(+), 5 deletions(-)
>  create mode 100644 t/t4013/diff.diff-tree_--root_-p_--abbrev=10_initial
>  create mode 100644 t/t4013/diff.diff-tree_--root_-p_--full-index_--abbrev=10_initial
>  create mode 100644 t/t4013/diff.diff-tree_--root_-p_--full-index_initial
> 
> diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
> index 7987d72b02..c11efa7865 100644
> --- a/Documentation/diff-options.txt
> +++ b/Documentation/diff-options.txt
> @@ -441,10 +441,11 @@ endif::git-format-patch[]
>  --abbrev[=<n>]::
>  	Instead of showing the full 40-byte hexadecimal object
>  	name in diff-raw format output and diff-tree header
> -	lines, show only a partial prefix.  This is
> -	independent of the `--full-index` option above, which controls
> -	the diff-patch output format.  Non default number of
> -	digits can be specified with `--abbrev=<n>`.
> +	lines, show only a partial prefix.
> +	In diff-patch output format, `--full-index` takes higher
> +	precedent, i.e. if `--full-index` is specified, full blob
> +	names will be shown regardless of `--abbrev`.
> +	Non default number of digits can be specified with `--abbrev=<n>`.
>  
>  -B[<n>][/<m>]::
>  --break-rewrites[=[<n>][/<m>]]::
> diff --git a/diff.c b/diff.c
> index f9709de7b4..20dedfe2a9 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -4319,7 +4319,10 @@ static void fill_metainfo(struct strbuf *msg,
>  	}
>  	if (one && two && !oideq(&one->oid, &two->oid)) {
>  		const unsigned hexsz = the_hash_algo->hexsz;
> -		int abbrev = o->flags.full_index ? hexsz : DEFAULT_ABBREV;
> +		int abbrev = o->abbrev ? o->abbrev : DEFAULT_ABBREV;
> +
> +		if (o->flags.full_index)
> +			abbrev = hexsz;
>  
>  		if (o->flags.binary) {
>  			mmfile_t mf;
> diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
> index 3f60f7d96c..e6eb4dd4c7 100755
> --- a/t/t4013-diff-various.sh
> +++ b/t/t4013-diff-various.sh
> @@ -221,6 +221,9 @@ diff-tree --root -r --abbrev=4 initial
>  :noellipses diff-tree --root -r --abbrev=4 initial
>  diff-tree -p initial
>  diff-tree --root -p initial
> +diff-tree --root -p --abbrev=10 initial
> +diff-tree --root -p --full-index initial
> +diff-tree --root -p --full-index --abbrev=10 initial
>  diff-tree --patch-with-stat initial
>  diff-tree --root --patch-with-stat initial
>  diff-tree --patch-with-raw initial
> diff --git a/t/t4013/diff.diff-tree_--root_-p_--abbrev=10_initial b/t/t4013/diff.diff-tree_--root_-p_--abbrev=10_initial
> new file mode 100644
> index 0000000000..7518a9044e
> --- /dev/null
> +++ b/t/t4013/diff.diff-tree_--root_-p_--abbrev=10_initial
> @@ -0,0 +1,29 @@
> +$ git diff-tree --root -p --abbrev=10 initial
> +444ac553ac7612cc88969031b02b3767fb8a353a
> +diff --git a/dir/sub b/dir/sub
> +new file mode 100644
> +index 0000000000..35d242ba79
> +--- /dev/null
> ++++ b/dir/sub
> +@@ -0,0 +1,2 @@
> ++A
> ++B
> +diff --git a/file0 b/file0
> +new file mode 100644
> +index 0000000000..01e79c32a8
> +--- /dev/null
> ++++ b/file0
> +@@ -0,0 +1,3 @@
> ++1
> ++2
> ++3
> +diff --git a/file2 b/file2
> +new file mode 100644
> +index 0000000000..01e79c32a8
> +--- /dev/null
> ++++ b/file2
> +@@ -0,0 +1,3 @@
> ++1
> ++2
> ++3
> +$
> diff --git a/t/t4013/diff.diff-tree_--root_-p_--full-index_--abbrev=10_initial b/t/t4013/diff.diff-tree_--root_-p_--full-index_--abbrev=10_initial
> new file mode 100644
> index 0000000000..69f913fbe5
> --- /dev/null
> +++ b/t/t4013/diff.diff-tree_--root_-p_--full-index_--abbrev=10_initial
> @@ -0,0 +1,29 @@
> +$ git diff-tree --root -p --full-index --abbrev=10 initial
> +444ac553ac7612cc88969031b02b3767fb8a353a
> +diff --git a/dir/sub b/dir/sub
> +new file mode 100644
> +index 0000000000000000000000000000000000000000..35d242ba79ae89ac695e26b3d4c27a8e6f028f9e
> +--- /dev/null
> ++++ b/dir/sub
> +@@ -0,0 +1,2 @@
> ++A
> ++B
> +diff --git a/file0 b/file0
> +new file mode 100644
> +index 0000000000000000000000000000000000000000..01e79c32a8c99c557f0757da7cb6d65b3414466d
> +--- /dev/null
> ++++ b/file0
> +@@ -0,0 +1,3 @@
> ++1
> ++2
> ++3
> +diff --git a/file2 b/file2
> +new file mode 100644
> +index 0000000000000000000000000000000000000000..01e79c32a8c99c557f0757da7cb6d65b3414466d
> +--- /dev/null
> ++++ b/file2
> +@@ -0,0 +1,3 @@
> ++1
> ++2
> ++3
> +$
> diff --git a/t/t4013/diff.diff-tree_--root_-p_--full-index_initial b/t/t4013/diff.diff-tree_--root_-p_--full-index_initial
> new file mode 100644
> index 0000000000..1b0b6717fa
> --- /dev/null
> +++ b/t/t4013/diff.diff-tree_--root_-p_--full-index_initial
> @@ -0,0 +1,29 @@
> +$ git diff-tree --root -p --full-index initial
> +444ac553ac7612cc88969031b02b3767fb8a353a
> +diff --git a/dir/sub b/dir/sub
> +new file mode 100644
> +index 0000000000000000000000000000000000000000..35d242ba79ae89ac695e26b3d4c27a8e6f028f9e
> +--- /dev/null
> ++++ b/dir/sub
> +@@ -0,0 +1,2 @@
> ++A
> ++B
> +diff --git a/file0 b/file0
> +new file mode 100644
> +index 0000000000000000000000000000000000000000..01e79c32a8c99c557f0757da7cb6d65b3414466d
> +--- /dev/null
> ++++ b/file0
> +@@ -0,0 +1,3 @@
> ++1
> ++2
> ++3
> +diff --git a/file2 b/file2
> +new file mode 100644
> +index 0000000000000000000000000000000000000000..01e79c32a8c99c557f0757da7cb6d65b3414466d
> +--- /dev/null
> ++++ b/file2
> +@@ -0,0 +1,3 @@
> ++1
> ++2
> ++3
> +$