gitk: Addressing error running on MacOS with large repos.

The change is stemmed from a problem on the MacOS where, if --all
is passed to gitk it should show all the refs/commits graphically.
However, on really large git repos, in my instance a git repo with
over 52,000 commits, gitk will report an error,
"Error executing git log: couldn't execute "git": argument list too long".
Mac OS has a limit of which my large repo exceeds. This works fine on Linux,
however, not sure about Windows.

Looking at gitk script, the decision to have all commit-ids on the command line
comes from return value of parseviewargs() function which uses the value of
"allknown" to return. If it is '1' then --all is translated to a string of all
the commit-ids in the repo, otherwise --all is passed as-is to `git log` cli,
which according to git-log man page it is the same as listing all the
commit-ids.

So, this change is to prevent --all option from being expanded into list
of all refs on the command line.

Signed-off-by: Arash Bannazadeh-Mahani <[email protected]>

Author: axbannaz

gitk-git/gitk

@@ -250,8 +250,13 @@ proc parseviewargs {n arglist} {
 		set nextisval 1
 		lappend glflags $arg
 	    }
-	    "--not" - "--all" {
+	    "--not" {
 		lappend revargs $arg
+	    }
+		"--all" {
+		# we recognize this argument;
+		# no expansion needed, use it with 'git log' as-is
+		set allknown 0
 	    }
 	    "--merge" {
 		set vmergeonly($n) 1