suggest make pack commit process timeout configurable

[comicfans]

gogs 0.11.29.0727
git version 2.15.0.windows.1
OS: win7 64
SQLite
can always reproduce the bug

Description

download release as zip in repository with many big binaries , gogs shows 500 page.

in log file, it shows:
routes/repo/repo.go:329 Download() CreateArchive xxxxx.zip execution is timeout [duration: 1m0s]

this always happened at first try, but for second time , it may success (maybe already in fs cache)

we have many binaries in repo and 1min is not enough, suggest make this value configurable

[comicfans]

DEFAULT_TIMEOUT = 60 * time.Second
at git-module/command.go:51