[PATCH v2] sub-process: print the cmd when a capability is unsupported

[Christian Couder <christian.couder@gmail.com>]

In handshake_capabilities() we use warning() when a capability
is not supported, so the exit code of the function is 0 and no
further error is shown. This is a problem because the warning
message doesn't tell us which subprocess cmd failed.

On the contrary if we cannot write a packet from this function,
we use error() and then subprocess_start() outputs:

    initialization for subprocess '<cmd>' failed

so we can know which subprocess cmd failed.

Let's improve the warning() message, so that we can know which
subprocess cmd failed.

Helped-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
Change since previous version:

  - Use process->argv[0] instead of adding a new parameter to
    handshake_capabilities(), thanks to Lars.

 sub-process.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sub-process.c b/sub-process.c
index 6edb97c1c6..6ccfaaba99 100644
--- a/sub-process.c
+++ b/sub-process.c
@@ -184,8 +184,8 @@ static int handshake_capabilities(struct child_process *process,
 			if (supported_capabilities)
 				*supported_capabilities |= capabilities[i].flag;
 		} else {
-			warning("external filter requested unsupported filter capability '%s'",
-				p);
+			warning("subprocess '%s' requested unsupported capability '%s'",
+				process->argv[0], p);
 		}
 	}
 
-- 
2.14.1.146.g7de11f915a