[PATCH] 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.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 sub-process.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/sub-process.c b/sub-process.c
index 6edb97c1c6..6b133f8dce 100644
--- a/sub-process.c
+++ b/sub-process.c
@@ -158,7 +158,8 @@ static int handshake_version(struct child_process *process,
 
 static int handshake_capabilities(struct child_process *process,
 				  struct subprocess_capability *capabilities,
-				  unsigned int *supported_capabilities)
+				  unsigned int *supported_capabilities,
+				  const char *cmd)
 {
 	int i;
 	char *line;
@@ -184,8 +185,8 @@ 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'",
+				cmd, p);
 		}
 	}
 
@@ -206,8 +207,10 @@ int subprocess_handshake(struct subprocess_entry *entry,
 
 	retval = handshake_version(process, welcome_prefix, versions,
 				   chosen_version) ||
-		 handshake_capabilities(process, capabilities,
-					supported_capabilities);
+		 handshake_capabilities(process,
+					capabilities,
+					supported_capabilities,
+					entry->cmd);
 
 	sigchain_pop(SIGPIPE);
 	return retval;
-- 
2.14.1.187.gd6d46550f4