Merge branch 'jk/xstrfmt' into next

Merge branch 'jk/xstrfmt' into next

* jk/xstrfmt:
  unique_path: fix unlikely heap overflow
  walker_fetch: fix minor memory leak
  merge: use argv_array when spawning merge strategy
  sequencer: use argv_array_pushf
  setup_git_env: use git_pathdup instead of xmalloc + sprintf
  use xstrfmt to replace xmalloc + strcpy/strcat
  use xstrfmt to replace xmalloc + sprintf
  use xstrdup instead of xmalloc + strcpy
  use xstrfmt in favor of manual size calculations
  strbuf: add xstrfmt helper