gitk: error on find

On GIT repository:

~/git$ git --version
git version 1.2.0
~/git$ gitk --all -d

if I search for "1.0.0" and hit "return", gitk gives:

error:

invalid command name "contmergediff"
invalid command name "contmergediff"
    while executing
"contmergediff $ids"
    (procedure "gettreediffline" line 14)
    invoked from within
"gettreediffline file5 c894168631e4b7da66ed3993a4c92380d38599a8"


...and goes to commit 8d712aafd2df3c1f5147a28947f98cefe667cf76, while the 
first commit containing "1.0.0" is c894168631e4b7da66ed3993a4c92380d38599a8

In general, pressing <return> instead of clicking "find", causes gitk to skip 
a commit (without other errors). This behaviour is present since (at last) 
GIT version 1.0.0.

Searching for "1.0.0" but clicking on "find" gives no errors.

I think "contmergediff" is an old procedure, but I don't know how to fix it 
(nor exactly what was meant to do). The error was first introduced with 
commit b77b02785d2f589ca336fc449ee1c27837263dac (it was a big change, so the 
"contmergediff" line was probably forgotten).