[PATCH] gitk: fix fatal error by dropping duplicated requests

[Max Kirillov <max@max630.net>]

During fast UI actions there may happen a fatal error message due to undefined
$blobdifffd($ids). It happens because 2 same requests happen to be started.
Then first one to complete wipes the $ids from blobdifffd, causing the second
to fail. Then no diff is displayed in that gitk process anymore, so it has
to be restarted. To reproduce one could fast click a big commit line twice, for
example, but I believe it is not the only case.

Fix by not starting a request if there is already one with the same $ids.
It does not seem to cause any malfunctioning when triggered.

Signed-off-by: Max Kirillov <max@max630.net>
---
 gitk | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/gitk b/gitk
index da84e22dd4..3919ba85b1 100755
--- a/gitk
+++ b/gitk
@@ -8009,6 +8009,10 @@ proc getblobdiffs {ids} {
     global limitdiffs vfilelimit curview
     global git_version
 
+    if {[info exists blobdifffd($ids)]} {
+	return
+    }
+
     set textconv {}
     if {[package vcompare $git_version "1.6.1"] >= 0} {
 	set textconv "--textconv"
@@ -9145,6 +9149,11 @@ proc do_cmp_commits {a b} {
 proc diffcommits {a b} {
     global diffcontext diffids blobdifffd diffinhdr currdiffsubmod
 
+    set diffids [list commits $a $b]
+    if {[info exists blobdifffd($diffids)]} {
+	return
+    }
+
     set tmpdir [gitknewtmpdir]
     set fna [file join $tmpdir "commit-[string range $a 0 7]"]
     set fnb [file join $tmpdir "commit-[string range $b 0 7]"]
@@ -9161,7 +9170,6 @@ proc diffcommits {a b} {
 	error_popup [mc "Error diffing commits: %s" $err]
 	return
     }
-    set diffids [list commits $a $b]
     set blobdifffd($diffids) $fd
     set diffinhdr 0
     set currdiffsubmod ""
-- 
2.19.0.1202.g68e1e8f04e