Re: [PATCH] log -L: improve error message on malformed argument

[Junio C Hamano <gitster@pobox.com>]

Matthieu Moy <Matthieu.Moy@imag.fr> writes:

> The old message did not mention the :regex:file form.
>
> To avoid overly long lines, split the message into two lines (in case
> item->string is long, it will be the only part truncated in a narrow
> terminal).
>
> Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
> ---
>  line-log.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/line-log.c b/line-log.c
> index a490efe..e725248 100644
> --- a/line-log.c
> +++ b/line-log.c
> @@ -575,7 +575,8 @@ parse_lines(struct commit *commit, const char *prefix, struct string_list *args)
>  
>  		name_part = skip_range_arg(item->string);
>  		if (!name_part || *name_part != ':' || !name_part[1])
> -			die("-L argument '%s' not of the form start,end:file",
> +			die("invalid -L argument '%s'.\n"
> +			    "It should be of the form start,end:file or :regex:file.",
>  			    item->string);
>  		range_part = xstrndup(item->string, name_part - item->string);
>  		name_part++;

I actually think "start,end:file" is more correct than your updated
text.

By adding :regex:file as a possibility, you are hinting that 'start'
and 'end' are *not* regular expressions but numbers, but

    $ git log -L'/^int main/,/^}/:git.c'

is a perfectly fine way to specify start (i.e. the first line that
matches '^int main') and end (i.e. the first line that matches '^}'
after that).  Perhaps rephrase it as :funcname:file to avoid giving
false impression to the other one, and use Eric's suggestion on top?

    die("-L argument not 'start,end:file' or ':funcname:file': %s",
	item->string);

With the matching update to tests, here is what I'll queue on top of
this patch for now, but please send in objections and improvements.

Thanks.

 line-log.c          | 3 +--
 t/t4211-line-log.sh | 8 ++++----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/line-log.c b/line-log.c
index 5d4cb7c..51d9f7c 100644
--- a/line-log.c
+++ b/line-log.c
@@ -543,8 +543,7 @@ parse_lines(struct commit *commit, const char *prefix, struct string_list *args)
 
 		name_part = skip_range_arg(item->string);
 		if (!name_part || *name_part != ':' || !name_part[1])
-			die("invalid -L argument '%s'.\n"
-			    "It should be of the form start,end:file or :regex:file.",
+			die("-L argument not 'start,end:file' or ':funcname:file': %s",
 			    item->string);
 		range_part = xstrndup(item->string, name_part - item->string);
 		name_part++;
diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index 426a828..edd5ed3 100755
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -40,14 +40,14 @@ canned_test "-L 24,+1:a.c simple" vanishes-early
 canned_test "-L '/long f/,/^}/:b.c' move-support" move-support-f
 
 test_bad_opts "-L" "switch.*requires a value"
-test_bad_opts "-L b.c" "argument.*not of the form"
-test_bad_opts "-L 1:" "argument.*not of the form"
+test_bad_opts "-L b.c" "argument not .start,end:file"
+test_bad_opts "-L 1:" "argument not .start,end:file"
 test_bad_opts "-L 1:nonexistent" "There is no path"
 test_bad_opts "-L 1:simple" "There is no path"
-test_bad_opts "-L '/foo:b.c'" "argument.*not of the form"
+test_bad_opts "-L '/foo:b.c'" "argument not .start,end:file"
 test_bad_opts "-L 1000:b.c" "has only.*lines"
 test_bad_opts "-L 1,1000:b.c" "has only.*lines"
-test_bad_opts "-L :b.c" "argument.*not of the form"
+test_bad_opts "-L :b.c" "argument not .start,end:file"
 test_bad_opts "-L :foo:b.c" "no match"
 
 test_done
-- 
2.4.0-rc2-183-g70401ab