diff --git a/libwyag.py b/libwyag.py
index 7d555b9..492e73b 100644
--- a/libwyag.py
+++ b/libwyag.py
@@ -643,8 +643,8 @@ def object_resolve(repo, name):
  - branches
  - remote branches"""
     candidates = list()
-    hashRE = re.compile(r"^[0-9A-Fa-f]{1,16}$")
-    smallHashRE = re.compile(r"^[0-9A-Fa-f]{1,16}$")
+    hashRE = re.compile(r"^[0-9A-Fa-f]{40}$")
+    smallHashRE = re.compile(r"^[0-9A-Fa-f]{4,20}$")
 
     # Empty string?  Abort.
     if not name.strip():
@@ -659,18 +659,18 @@ def object_resolve(repo, name):
         if len(name) == 40:
             # This is a complete hash
             return [ name.lower() ]
-        elif len(name) >= 4:
-            # This is a small hash 4 seems to be the minimal length
-            # for git to consider something a short hash.
-            # This limit is documented in man git-rev-parse
-            name = name.lower()
-            prefix = name[0:2]
-            path = repo_dir(repo, "objects", prefix, mkdir=False)
-            if path:
-                rem = name[2:]
-                for f in os.listdir(path):
-                    if f.startswith(rem):
-                        candidates.append(prefix + f)
+    elif smallHashRE.match(name):
+        # This is a small hash 4 seems to be the minimal length
+        # for git to consider something a short hash.
+        # This limit is documented in man git-rev-parse
+        name = name.lower()
+        prefix = name[0:2]
+        path = repo_dir(repo, "objects", prefix, mkdir=False)
+        if path:
+            rem = name[2:]
+            for f in os.listdir(path):
+                if f.startswith(rem):
+                    candidates.append(prefix + f)
 
     return candidates
 
diff --git a/write-yourself-a-git.org b/write-yourself-a-git.org
index e7408cc..9d24301 100644
--- a/write-yourself-a-git.org
+++ b/write-yourself-a-git.org
@@ -1794,8 +1794,8 @@ referred to as =5bd254=.  This is called a "short hash".
    - branches
    - remote branches"""
       candidates = list()
-      hashRE = re.compile(r"^[0-9A-Fa-f]{1,16}$")
-      smallHashRE = re.compile(r"^[0-9A-Fa-f]{1,16}$")
+      hashRE = re.compile(r"^[0-9A-Fa-f]{40}$")
+      smallHashRE = re.compile(r"^[0-9A-Fa-f]{4,20}$")
 
       # Empty string?  Abort.
       if not name.strip():
@@ -1810,18 +1810,18 @@ referred to as =5bd254=.  This is called a "short hash".
           if len(name) == 40:
               # This is a complete hash
               return [ name.lower() ]
-          elif len(name) >= 4:
+      elif smallHashRE.match(name):
               # This is a small hash 4 seems to be the minimal length
               # for git to consider something a short hash.
               # This limit is documented in man git-rev-parse
-              name = name.lower()
-              prefix = name[0:2]
-              path = repo_dir(repo, "objects", prefix, mkdir=False)
-              if path:
-                  rem = name[2:]
-                  for f in os.listdir(path):
-                      if f.startswith(rem):
-                          candidates.append(prefix + f)
+          name = name.lower()
+          prefix = name[0:2]
+          path = repo_dir(repo, "objects", prefix, mkdir=False)
+          if path:
+              rem = name[2:]
+              for f in os.listdir(path):
+                  if f.startswith(rem):
+                      candidates.append(prefix + f)
 
       return candidates
 #+END_SRC
@@ -1970,6 +1970,53 @@ holds quite a lot of stuff:
       name = None
 #+END_SRC
 
+* Running the executable
+
+Remember when we ran this command?
+
+#+BEGIN_EXAMPLE
+  $ chmod +x wyag
+#+END_EXAMPLE
+
+We will now build the project so you can run it from anywhere just like Git.
+
+First create a setup.py file.
+
+We will use a library called setuptools.
+
+#+BEGIN_SRC python :tangle libwyag.py
+import setuptools
+
+setuptools.setup(
+    name='wyag',
+    version='1.0',
+    author='Thibault Polge',
+    author_email='thibault@thb.lt',
+    description='Write Yourself a Git!',
+    packages=setuptools.find_packages(),
+    scripts=['wyag'],
+    classifiers=[
+        'Programming Language :: Python :: 3',
+        'License :: OSI Approved :: MIT License',
+        'Operating System :: OS Independent',
+    ],
+)
+#+END_SRC
+
+You can now build the project:
+
+#+BEGIN_EXAMPLE
+   $ sudo python3 setup.py install
+#+END_EXAMPLE
+
+And use wyag globally (from any path) like this:
+
+#+BEGIN_EXAMPLE
+   $ wyag --help
+#+END_EXAMPLE
+
+Note: If you have structured your code in folders then remember to include an empty __init__.py in every folder.
+
 * Final words
 
 ** Comments, feedback and issues