The Apple Dumpling Gang Rides Again (1979) on Netflix

Plot summary

Amos Tucker and Theodore Ogelvie, two bumbling holdup men, have decided to go straight and ride into the boom town of Junction City to begin again. There robbers Wes Hardin and Hank Starrett cheat them out of their money, and the robbery is blamed on Amos and Theodore, who flee. Junction City's feared lawman, Marshal Woolly Bill Hitchcock, nurses a personal grudge: Amos and Theodore humiliated and injured him twice by accident. The two abandon their donkey Clarise, which the robbers had used, and enlist in the United States Cavalry at Fort Concho, where the commander, Major Gaskill, is losing his supplies to a thief.