Add git blob hash to version cmd (#683)

This is useful for finding which commit a 'standalone' GEF install was installed from.

docs/commands/version.md

@@ -0,0 +1,34 @@
+## Command version ##
+
+Print out version information about your current gdb environment.
+
+### Usage Examples ###
+
+When GEF is located in a directory tracked with git:
+
+```
+gef➤  version
+GEF: rev:48a9fd74dd39db524fb395e7db528f85cc49d081 (Git - clean)
+SHA1(/gef/rules/gef.py): 848cdc87ba7c3e99e8129ad820c9fcc0973b1e99
+GDB: 9.2
+GDB-Python: 3.8
+```
+
+Otherwise the command shows the `standalone` information:
+
+```
+gef➤  aslr on
+GEF: (Standalone)
+Blob Hash(/gef/rules/gef.py): 2939fbc037bca090422e12cf1b555bd58223dccb
+SHA1(/gef/rules/gef.py): 6e6bfd03282a0d5b1eec5276fa57af0ccbac31c6
+GDB: 9.2
+GDB-Python: 3.8
+```
+
+The `Blob Hash` can be used to easily find the git commit(s) matching
+this file revision (or whether it has been modified and does not match
+any revision):
+
+```
+git log --oneline --find-object <BLOB_HASH>
+```

gef.py

@@ -4319,11 +4319,13 @@ def do_invoke(self, argv):
         gef_hash = hashlib.sha1(open(gef_fpath, "rb").read()).hexdigest()
 
         if os.access("{}/.git".format(gef_dir), os.X_OK):
-            ver = subprocess.check_output('git log --format="%H" -n 1 HEAD', cwd=gef_dir, shell=True).decode("utf8").strip()
-            extra = "dirty" if len(subprocess.check_output('git ls-files -m', cwd=gef_dir, shell=True).decode("utf8").strip()) else "clean"
+            ver = subprocess.check_output("git log --format='%H' -n 1 HEAD", cwd=gef_dir, shell=True).decode("utf8").strip()
+            extra = "dirty" if len(subprocess.check_output("git ls-files -m", cwd=gef_dir, shell=True).decode("utf8").strip()) else "clean"
             gef_print("GEF: rev:{} (Git - {})".format(ver, extra))
         else:
+            gef_blob_hash = subprocess.check_output("git hash-object {}".format(gef_fpath), shell=True).decode().strip()
             gef_print("GEF: (Standalone)")
+            gef_print("Blob Hash({}): {}".format(gef_fpath, gef_blob_hash))
         gef_print("SHA1({}): {}".format(gef_fpath, gef_hash))
         gef_print("GDB: {}".format(gdb.VERSION, ))
         py_ver = "{:d}.{:d}".format(sys.version_info.major, sys.version_info.minor)

mkdocs.yml

@@ -56,6 +56,7 @@ nav:
 - Command tmux-setup: commands/tmux-setup.md
 - Command trace-run: commands/trace-run.md
 - Command unicorn-emulate: commands/unicorn-emulate.md
+- Command version: commands/version.md
 - Command vmmap: commands/vmmap.md
 - Command xfiles: commands/xfiles.md
 - Command xinfo: commands/xinfo.md