Modify create_tag : verifications are now done in an another function
Modify create_tag : verifications are now done in an another function

This commit create a function called tag_valid_in_odb which validate a
tag before its creation. This function will be needed by my next commit.

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