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(In [3249]) GitPlugin: backport fix for get_changes() from 0.11 branch (addresses #2602)

I hope that [3249] fixes this issue;

as for zip files, I experienced an issue with python 2.5's zipfile module, which changed the zip-creator-system to unix, and then caused trac-generated zip file to have no unix permissions set (= empty permissions), e.g.

zipinfo changeset_r63b4b8213fabc5a57f897b60b6eaa9f78d86e6ff.zip 
Archive:  changeset_r63b4b8213fabc5a57f897b60b6eaa9f78d86e6ff.zip   50688   11
?---------  2.0 unx     9365 b- defN 11-Jan-08 13:31 configure.ac
?---------  2.0 unx     6892 b- defN 11-Jan-08 13:31 src/Makefile.am
?---------  2.0 unx    22650 b- defN 11-Jan-08 13:31 src/ati.c
?---------  2.0 unx    21039 b- defN 11-Jan-08 13:31 src/aticonsole.c
?---------  2.0 unx    11110 b- defN 11-Jan-08 13:31 src/atii2c.c
?---------  2.0 unx     2875 b- defN 11-Jan-08 13:31 src/atiload.c
?---------  2.0 unx     1421 b- defN 11-Jan-08 13:31 src/atiload.h
?---------  2.0 unx     3352 b- defN 11-Jan-08 13:31 src/atimisc.c
?---------  2.0 unx    34685 b- defN 11-Jan-08 13:31 src/atimode.c
?---------  2.0 unx     2182 b- defN 11-Jan-08 13:31 src/atimodule.c
?---------  2.0 unx    89363 b- defN 11-Jan-08 13:31 src/atipreinit.c
11 files, 204934 bytes uncompressed, 49536 bytes compressed:  75.8%

as opposed to what python 2.4's zipfile module would generate with trac (notice the fat vs unx; calling zipinfo with -v would show it even more verbose...):

zipinfo changeset_r6537.zip 
Archive:  changeset_r6537.zip   4006 bytes   1 file
-rw----     2.0 fat    12947 b- defN 18-Feb-08 11:01 /trunk/trac/timeline/web_ui.py
1 file, 12947 bytes uncompressed, 3848 bytes compressed:  70.3%

see also trac:ticket:6851