Re: git-rerere observations and feature suggestions

* Ingo Molnar [off-list ref] wrote:

And while asking for an arm i'd also like to ask for a leg, if i may: 
i'd love it if a "slightly conflicting" octopus merge of 85 topic 
trees would not result in one huge conflict commit that merges 
together 1000 commits into a single commit ;-)

So right now in our -tip scripts work around this issue: we 
'serialize' the topic merges despite having very nice opportunities 
for higher-order octopus merges. The integration would be a lot faster 
if we could use octopus merges and automated git-rerere. (Octopus 
merges would look much nicer as well in graphical representation as 
well, which counts too :-) )

just to demonstrate it, i tried today to do an octopus merge of 87 topic 
branches:

git-merge build checkme core/checkme core/debugobjects core/futex-64bit 
core/iter-div core/kill-the-BKL core/locking core/misc core/percpu 
core/printk core/rcu core/rodata core/softirq core/softlockup 
core/stacktrace core/topology core/urgent cpus4096 genirq kmemcheck 
kmemcheck2 mm/xen out-of-tree pci-for-jesse safe-poison-pointers sched 
sched-devel scratch stackprotector timers/clockevents timers/hpet 
timers/hrtimers timers/nohz timers/posixtimers tip tracing/ftrace 
tracing/ftrace-mergefixups tracing/immediates tracing/markers 
tracing/mmiotrace tracing/mmiotrace-mergefixups tracing/nmisafe 
tracing/sched_markers tracing/stopmachine-allcpus tracing/sysprof 
tracing/textedit x86/apic x86/apm x86/bitops x86/build x86/checkme 
x86/cleanups x86/cpa x86/cpu x86/defconfig x86/delay x86/gart x86/i8259 
x86/idle x86/intel x86/irq x86/irqstats x86/kconfig x86/ldt x86/mce 
x86/memtest x86/mmio x86/mpparse x86/nmi x86/numa x86/numa-fixes x86/pat 
x86/pebs x86/ptemask x86/resumetrace x86/scratch x86/setup x86/smpboot 
x86/threadinfo x86/timers x86/urgent x86/urgent-undo-ioapic x86/uv 
x86/vdso x86/xen x86/xsave

it failed miserably:

 warning: ignoring 066519068ad2fbe98c7f45552b1f592903a9c8c8; cannot 
 handle more than 25 refs
 [...]
 fatal: merge program failed
 Automated merge did not work.
 Should not be doing an Octopus.
 Merge with strategy octopus failed.

this wasnt even for purposes of an integration run: all i wanted to do 
was to pick up 2-3 new commits i have queued into 2-3 topic branches, 
into the (throw-away) integration branch. All the other branches were 
unmodified and already merged into the integration branch.

Hence i believe that the suggestions above by Git that i'm doing 
something wrong are ... wrong :-)

My scripting around this would be a lot faster (less than 10 seconds 
runtime versus a minute currently) and more robust if we could do such 
higher-order octopus merges.

	Ingo