see also issue839.

Closing this as a Python bug.

http://selenic.com/hg/rev/fe41d9a186ab lets you work around this.

http://mail.python.org/pipermail/python-bugs-list/2007-March/037810.html

maybe this is the cause: http://mail.python.org/pipermail/python-bugs-
list/2007-March/037810.html ?

should we close it as python bug?

the error is not alsways "The filename or extension is too long:", but might 
also be:
abort: The system cannot find the path specified:

not sure when happens what.

it seems that mercurial is able to create longer filenames that are supported. 
with normal windows tools it is not possible to remove them.

C:\tmp\hg-test\really-long-name-or-what>hg add
adding processes_is-it-true-
this_is_closing_factory_process_V4_LONG_Test_Admin_UNICEF_AJO_LONGER_TER_Prep_T
EV_Results_UN
IL_Auto_TTT_Prep_JAPAN_Check_Autonomation_Errors.ita

C:\tmp\hg-test\really-long-name-or-what>hg commit
trouble committing processes_is-it-true-
this_is_closing_factory_process_V4_LONG_Test_Admin_UNICEF_AJO_LONGER_TER_Prep_T
E
V_Results_UNIL_Auto_TTT_Prep_JAPAN_Check_Autonomation_Errors.ita!
abort: The filename or extension is too long: C:\tmp\hg-test\really-long-name-
or-what\.hg\store\data/processes__is-it-tr
ue-
this__is__closing__factory__process___v4___l_o_n_g___test___admin___u_n_i_c_e_f
___a_j_o___l_o_n_g_e_r___t_e_r___prep_
__t_e_v___results___u_n_i_l___auto___t_t_t___prep___j_a_p_a_n___check___autonom
ation___errors.ita.i