https://forum.freecadweb.org/viewtopic.php?f=22&t=40299&p=342660

AddonMangerHeadless.py

# -*- coding: utf-8 -*-
# FreeCAD Headless AddonManager test
# (c) 2019 FreeCAD community LGPL

"""
The module can be executed with:
./FreeCAD.AppImage -c <path_to_file> AddonManagerHeadless.py

Note:
In order to test updates, it possible to use git reset --hard HEAD~1
which will rollback a repo 1 commit behind master.
"""

import os, re, shutil, stat, sys, tempfile
import pdb  # python debugger
import git, readline
import FreeCAD
import addonmanager_utilities as utils

# Blacklisted addons
MACROS_BLACKLIST = ["BOLTS",
                    "WorkFeatures",
                    "how to install",
                    "PartsLibrary",
                    "FCGear"]

# These addons will print an additional message informing the user
OBSOLETE =         ["assembly2",
                    "drawing_dimensioning",
                    "cura_engine"]

NOGIT = False # for debugging purposes, set this to True to always use http downloads

def ListRepo():
    u = utils.urlopen("https://github.com/FreeCAD/FreeCAD-addons")

    if not u:
        print("Unable to open URL")
        quit()
    p = u.read()

    if sys.version_info.major >= 3 and isinstance(p, bytes):
        p = p.decode("utf-8")
    u.close()

    p = p.replace("\n"," ")
    p = re.findall("octicon-file-submodule(.*?)message",p)
    basedir = FreeCAD.getUserAppDataDir()
    moddir = basedir + os.sep + "Mod"
    repos = []
    # querying official addons
    for l in p:
        #name = re.findall("data-skip-pjax=\"true\">(.*?)<",l)[0]
        res = re.findall("title=\"(.*?) @",l)
        if res:
            name = res[0]
        else:
            print("AddonMananger: Debug: couldn't find title in",l)
            continue
        # Print repo name by itself
        # print(name)
        #url = re.findall("title=\"(.*?) @",l)[0]
        url = utils.getRepoUrl(l)
        if url:
            addondir = moddir + os.sep + name
            #print ("found:",name," at ",url)
            if os.path.exists(addondir) and os.listdir(addondir):
                # make sure the folder exists and it contains files!
                state = 1
            else:
                state = 0
            repos.append([name,url,state])
    # querying custom addons
    # customaddons = FreeCAD.ParamGet("User parameter:BaseApp/Preferences/Addons").GetString("CustomRepositories","").split("\n")
    # for url in customaddons:
    #     if url:
    #         name = url.split("/")[-1]
    #         if name.lower().endswith(".git"):
    #             name = name[:-4]
    #         addondir = moddir + os.sep + name
    #         if not os.path.exists(addondir):
    #             sfor repo in repos:tate = 0
    #         else:
    #             state = 1
    #         repos.append([name,url,state])
    if not repos:
        print("Unable to download addon list.")
    else:
        repos = sorted(repos, key=lambda s: s[0].lower())
        print("List official available Addons:\n")
        for repo in repos:
            # addon installed
            if repo[2] == 1:
                # distinguish w/ preceding '+'
                print(' +\t' + repo[0])
            # addom not installed
            if repo[2] == 0:
                # distinguish w/ preceding 'x'
                print('x\t' + repo[0])
        # print a legend 
        print('\nLegend:\n+ = Installed\nx = Not Installed\n')

        # just show what addons are installed
        print('Currently installed Addons:')
        for repo in repos:
            if repo[2] == 1:
                print('\t'+repo[0])
        return(repos)

def CheckUpdateRepo(repos):
    basedir = FreeCAD.getUserAppDataDir()
    moddir = basedir + os.sep + "Mod"
    # upds = []  # store updates
    for repo in repos:
        if repo[2] == 1:
            print("Checking updates for",repo[0])
            clonedir = moddir + os.sep + repo[0]
            # if os.path.exists(clonedir):
                # # check if this addon was not installed with git
                # if not os.path.exists(clonedir + os.sep + '.git'):
                #     # It wasn't, therefore repair addon installed with raw download
                #     # creating a git.Repo object to represent repo
                #     bare_repo = git.Repo.clone_from(repo[1], clonedir + os.sep + '.git', bare=True)
                #     try:
                #         with bare_repo.config_writer() as cw:
                #             cw.set('core', 'bare', False)
                #     except AttributeError:
                #         if not gitpython_warning:
                #             print('Outdated GitPython detected, consider upgrading with pip')
                #             gitpython_warning = True
                #         cw = bare_repo.config_writer()
                #         cw.set('core', 'bare', False)
                #         del cw
                #     repo = git.Repo(clonedir)
                #     repo.head.reset('--hard')
                # clone the addon repo
            gitrepo = git.Git(clonedir)
            try:
                gitrepo.fetch()
                # TODO: (?) write a little regex for "Your branch is up to date"
                # print(gitrepo.status()+'\n')
                repos[repos.index(repo)][2] = 2 # mark as already installed AND already checked for updates
                # pdb.set_trace() # breakpoint
            except:
                print("AddonManager: Unable to fetch git updates for repo",repo[0])
            else:
                # pdb.set_trace() # breakpoint
                # 'git status' will tell us if we need to 'git pull'
                # note: print(gitrepo.status()) for troubleshooting
                if "git pull" in gitrepo.status():
                    print('\t' + repo[0] + ' ' + 'has an update')
                    status = re.findall(r"Your branch (.*)\,", gitrepo.status())
                    print('\t' + repo[0] + ' ' + status[0] + '\n')
                    # upds.append(repo) # not sure this is necessary due to:
                    repos[repos.index(repo)][2] = 3 # mark as already installed AND already checked for updates
                    # pdb.set_trace() # breakpoint
    return(repos)

def UpdateRepo(repos):

    '''installs or updates the selected addons'''

    basedir = FreeCAD.getUserAppDataDir()
    moddir = basedir + os.sep + "Mod"   
    if not os.path.exists(moddir):
        os.makedirs(moddir)
    for repo in repos:
        if repo[2] == 3: # installed but has an update pending
            clonedir = moddir + os.sep + repo[0]
            if os.path.exists(clonedir):
                print('Updating ' + repo[0] + ' addon...')
                # first check if the addon was originally downloaded as a zip 
                if not os.path.exists(clonedir + os.sep + '.git'):
                    # Repair addon installed with raw download
                    bare_repo = git.Repo.clone_from(repo[1], clonedir + os.sep + '.git', bare=True)
                    try:
                        with bare_repo.config_writer() as cw:
                            cw.set('core', 'bare', False)
                    except AttributeError:
                        print("Outdated GitPython detected, consider upgrading with pip.")
                        cw = bare_repo.config_writer()
                        cw.set('core', 'bare', False)
                        del cw
                    repo = git.Repo(clonedir)
                    repo.head.reset('--hard')
                repo = git.Git(clonedir)
                try:
                    answer = repo.pull()
                except:
                    print("Error updating module ",repo[1]," - Please fix manually")
                    answer = repo.status()
                    print(answer)
                else:
                    # Update the submodules for this repository
                    repo_sms = git.Repo(clonedir)
                    for submodule in repo_sms.submodules:
                        submodule.update(init=True, recursive=True)
        else:
            pass
    return(repos)




def CheckUpdate(name):
    """Check for updates for a single addon"""

    updateAvailable = ''

    # do we have GitPython?
    try:
        import git
    except:
        #return
        print('No GitPython installed...aborting')
        quit()
    print("Checking for available updates of the "+name+" addon")
    # construct the local addon directory location
    addondir = os.path.join(FreeCAD.getUserAppDataDir(),"Mod",name)
    if os.path.exists(addondir):
        if os.path.exists(addondir + os.sep + '.git'):
            # local addon dir exists
            gitrepo = git.Git(addondir)
            try:
                # lets pull any new updates
                gitrepo.fetch()
                if "git pull" in gitrepo.status():
                    updateAvailable(True)
                    return
            except:
                # can fail for any number of reasons, ex. not being online
                pass
    updateAvailable(False)


if __name__ == '__main__':
    repos = ListRepo()
    print('\nCheckUpdateRepo()\n')
    # pdb.set_trace() # breakpoint
    repos = CheckUpdateRepo(repos)
    # pdb.set_trace() # breakpoint
    repos = UpdateRepo(repos)
    # pdb.set_trace() # breakpoint