git p4: catch p4 describe errors

Group the two calls to "p4 describe" into a new helper function,
and try to validate the p4 results.  The current behavior when p4
describe fails is to die with a python backtrace.  The new behavior
will print the full response.

This does not solve any particular problem, but adds more
checking in hopes of narrowing down odd behavior seen on
at least two occasions.
Based-on-patch-by: NMatt Arsenault <arsenm2@gmail.com>
Reported-by: NArthur <a.foulon@amesys.fr>
Signed-off-by: NPete Wyckoff <pw@padd.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

git-p4.py

@@ -169,6 +169,29 @@ def p4_reopen(type, f):
 def p4_move(src, dest):
     p4_system(["move", "-k", wildcard_encode(src), wildcard_encode(dest)])
 
+def p4_describe(change):
+    """Make sure it returns a valid result by checking for
+       the presence of field "time".  Return a dict of the
+       results."""
+
+    ds = p4CmdList(["describe", "-s", str(change)])
+    if len(ds) != 1:
+        die("p4 describe -s %d did not return 1 result: %s" % (change, str(ds)))
+
+    d = ds[0]
+
+    if "p4ExitCode" in d:
+        die("p4 describe -s %d exited with %d: %s" % (change, d["p4ExitCode"],
+                                                      str(d)))
+    if "code" in d:
+        if d["code"] == "error":
+            die("p4 describe -s %d returned error code: %s" % (change, str(d)))
+
+    if "time" not in d:
+        die("p4 describe -s %d returned no \"time\": %s" % (change, str(d)))
+
+    return d
+
 #
 # Canonicalize the p4 type and return a tuple of the
 # base type, plus any modifiers.  See "p4 help filetypes"
@@ -2543,7 +2566,7 @@ def searchParent(self, parent, branch, target):
     def importChanges(self, changes):
         cnt = 1
         for change in changes:
-            description = p4Cmd(["describe", str(change)])
+            description = p4_describe(change)
             self.updateOptionDict(description)
 
             if not self.silent:
@@ -2667,14 +2690,8 @@ def importHeadRevision(self, revision):
 
         # Use time from top-most change so that all git p4 clones of
         # the same p4 repo have the same commit SHA1s.
-        res = p4CmdList("describe -s %d" % newestRevision)
-        newestTime = None
-        for r in res:
-            if r.has_key('time'):
-                newestTime = int(r['time'])
-        if newestTime is None:
-            die("\"describe -s\" on newest change %d did not give a time")
-        details["time"] = newestTime
+        res = p4_describe(newestRevision)
+        details["time"] = res["time"]
 
         self.updateOptionDict(details)
         try: