Update showindex example
Update showindex example

I find the showindex example to be pretty useful on occasion, but
there were are couple of output tweaks I wanted, plus I wanted the
ability to specify a path to an actual index file instead of having
to open the whole repository.  This makes those changes and expands
the example slightly.

oaastest/libgit2,leoyanggit/libgit2,nokiddin/libgit2,swisspol/DEMO-libgit2,mhp/libgit2,t0xicCode/libgit2,jflesch/libgit2-mariadb,skabel/manguse,Snazz2001/libgit2,skabel/manguse,Corillian/libgit2,Snazz2001/libgit2,jeffhostetler/public_libgit2,leoyanggit/libgit2,swisspol/DEMO-libgit2,iankronquist/libgit2,MrHacky/libgit2,mhp/libgit2,stewid/libgit2,Snazz2001/libgit2,magnus98/TEST,saurabhsuniljain/libgit2,nokiddin/libgit2,since2014/libgit2,sygool/libgit2,falqas/libgit2,rcorre/libgit2,kenprice/libgit2,mhp/libgit2,since2014/libgit2,mhp/libgit2,amyvmiwei/libgit2,kenprice/libgit2,MrHacky/libgit2,since2014/libgit2,Aorjoa/libgit2_maked_lib,magnus98/TEST,linquize/libgit2,yosefhackmon/libgit2,whoisj/libgit2,iankronquist/libgit2,mingyaaaa/libgit2,falqas/libgit2,nokiddin/libgit2,t0xicCode/libgit2,jflesch/libgit2-mariadb,yongthecoder/libgit2,amyvmiwei/libgit2,raybrad/libit2,oaastest/libgit2,Aorjoa/libgit2_maked_lib,yongthecoder/libgit2,kissthink/libgit2,dleehr/libgit2,chiayolin/libgit2,chiayolin/libgit2,skabel/manguse,sim0629/libgit2,iankronquist/libgit2,jeffhostetler/public_libgit2,whoisj/libgit2,skabel/manguse,maxiaoqian/libgit2,saurabhsuniljain/libgit2,mcanthony/libgit2,mcanthony/libgit2,mingyaaaa/libgit2,evhan/libgit2,skabel/manguse,spraints/libgit2,ardumont/libgit2,yongthecoder/libgit2,raybrad/libit2,iankronquist/libgit2,MrHacky/libgit2,sygool/libgit2,JIghtuse/libgit2,spraints/libgit2,mhp/libgit2,linquize/libgit2,saurabhsuniljain/libgit2,iankronquist/libgit2,Tousiph/Demo1,kissthink/libgit2,sim0629/libgit2,nokiddin/libgit2,magnus98/TEST,spraints/libgit2,MrHacky/libgit2,kissthink/libgit2,Corillian/libgit2,mcanthony/libgit2,yosefhackmon/libgit2,evhan/libgit2,ardumont/libgit2,linquize/libgit2,JIghtuse/libgit2,jeffhostetler/public_libgit2,claudelee/libgit2,sim0629/libgit2,sim0629/libgit2,mingyaaaa/libgit2,maxiaoqian/libgit2,joshtriplett/libgit2,dleehr/libgit2,Snazz2001/libgit2,t0xicCode/libgit2,jamieleecool/ptest,jeffhostetler/public_libgit2,yosefhackmon/libgit2,jflesch/libgit2-mariadb,KTXSoftware/libgit2,jeffhostetler/public_libgit2,sygool/libgit2,MrHacky/libgit2,zodiac/libgit2.js,sim0629/libgit2,rcorre/libgit2,mrksrm/Mingijura,zodiac/libgit2.js,whoisj/libgit2,Tousiph/Demo1,claudelee/libgit2,ardumont/libgit2,Tousiph/Demo1,falqas/libgit2,yosefhackmon/libgit2,kissthink/libgit2,Corillian/libgit2,spraints/libgit2,yongthecoder/libgit2,mcanthony/libgit2,amyvmiwei/libgit2,jamieleecool/ptest,JIghtuse/libgit2,magnus98/TEST,yosefhackmon/libgit2,chiayolin/libgit2,joshtriplett/libgit2,maxiaoqian/libgit2,rcorre/libgit2,sygool/libgit2,jflesch/libgit2-mariadb,Tousiph/Demo1,oaastest/libgit2,evhan/libgit2,kenprice/libgit2,ardumont/libgit2,swisspol/DEMO-libgit2,t0xicCode/libgit2,joshtriplett/libgit2,chiayolin/libgit2,Snazz2001/libgit2,Tousiph/Demo1,magnus98/TEST,sim0629/libgit2,kissthink/libgit2,saurabhsuniljain/libgit2,Corillian/libgit2,whoisj/libgit2,maxiaoqian/libgit2,jflesch/libgit2-mariadb,mrksrm/Mingijura,raybrad/libit2,dleehr/libgit2,falqas/libgit2,stewid/libgit2,jamieleecool/ptest,mrksrm/Mingijura,since2014/libgit2,mrksrm/Mingijura,spraints/libgit2,JIghtuse/libgit2,mrksrm/Mingijura,whoisj/libgit2,stewid/libgit2,amyvmiwei/libgit2,amyvmiwei/libgit2,yosefhackmon/libgit2,KTXSoftware/libgit2,swisspol/DEMO-libgit2,oaastest/libgit2,ardumont/libgit2,claudelee/libgit2,linquize/libgit2,Corillian/libgit2,falqas/libgit2,jeffhostetler/public_libgit2,KTXSoftware/libgit2,ardumont/libgit2,zodiac/libgit2.js,oaastest/libgit2,mcanthony/libgit2,claudelee/libgit2,zodiac/libgit2.js,swisspol/DEMO-libgit2,rcorre/libgit2,kissthink/libgit2,linquize/libgit2,claudelee/libgit2,chiayolin/libgit2,MrHacky/libgit2,maxiaoqian/libgit2,falqas/libgit2,mcanthony/libgit2,mrksrm/Mingijura,KTXSoftware/libgit2,leoyanggit/libgit2,raybrad/libit2,saurabhsuniljain/libgit2,chiayolin/libgit2,amyvmiwei/libgit2,stewid/libgit2,Aorjoa/libgit2_maked_lib,maxiaoqian/libgit2,magnus98/TEST,evhan/libgit2,zodiac/libgit2.js,dleehr/libgit2,nokiddin/libgit2,rcorre/libgit2,KTXSoftware/libgit2,swisspol/DEMO-libgit2,joshtriplett/libgit2,joshtriplett/libgit2,Tousiph/Demo1,whoisj/libgit2,linquize/libgit2,JIghtuse/libgit2,yongthecoder/libgit2,Aorjoa/libgit2_maked_lib,claudelee/libgit2,skabel/manguse,since2014/libgit2,leoyanggit/libgit2,t0xicCode/libgit2,JIghtuse/libgit2,yongthecoder/libgit2,jamieleecool/ptest,leoyanggit/libgit2,spraints/libgit2,t0xicCode/libgit2,mingyaaaa/libgit2,stewid/libgit2,stewid/libgit2,leoyanggit/libgit2,kenprice/libgit2,Snazz2001/libgit2,kenprice/libgit2,raybrad/libit2,kenprice/libgit2,joshtriplett/libgit2,mingyaaaa/libgit2,since2014/libgit2,mingyaaaa/libgit2,mhp/libgit2,saurabhsuniljain/libgit2,dleehr/libgit2,jflesch/libgit2-mariadb,sygool/libgit2,sygool/libgit2,Aorjoa/libgit2_maked_lib,dleehr/libgit2,rcorre/libgit2,oaastest/libgit2,nokiddin/libgit2,Corillian/libgit2,KTXSoftware/libgit2,iankronquist/libgit2