fix(bin/git-browse): fix commit hash

Retrieving commit hashes with the following command is not very reliable for
users who sign their commits with gpg/ssh keys:

```
git log -n1 --format=format:"%H" "${filename}" 2>/dev/null
```

bin/git-browse

@@ -8,7 +8,7 @@ line2=${4:-""}
 
 # get remote name
 if [[ $remote == "" ]]; then
-    branch=$(git rev-parse --abbrev-ref HEAD 2 &>/dev/null)
+    branch="$(git rev-parse --abbrev-ref HEAD 2>/dev/null)"
     remote=$(git config branch."${branch}".remote || echo "origin")
 fi
 
@@ -31,14 +31,14 @@ elif [[ $remote_url = http* ]]; then
 fi
 
 # construct urls
-commit_hash=$(git log -n1 --format=format:"%H" "${filename}" 2>/dev/null)
+commit_hash=$(git rev-parse HEAD 2>/dev/null)
 commit_or_branch=${commit_hash:-${branch}}
 
 if [[ $remote_url =~ gitlab ]]; then
     # construct gitlab urls
     # https://gitlab.com/<user_or_group>/<repo>/-/blob/<commit_or_branch>/<filename>#L<line1>-<line2>
     if [[ -n ${filename} ]]; then
-        url="${url}/-/blob/${commit_hash:-${branch}}/${filename}"
+        url="${url}/-/blob/${commit_or_branch}/${filename}"
         if [[ -n "${line1}" ]]; then
             url="${url}#L${line1}"
             if [[ -n "${line2}" ]]; then
@@ -50,7 +50,7 @@ elif [[ $remote_url =~ github ]]; then
     # construct github urls
     # https://github.com/<user_or_org>/<repo>/blob/<commit_or_branch>/<filename>#L<line1>-L<line2>
     if [[ -n "${filename}" ]]; then
-        url="${url}/blob/${commit_hash:-${branch}}/${filename}"
+        url="${url}/blob/${commit_or_branch}/${filename}"
         if [[ -n "${line1}" ]]; then
             url="${url}#L${line1}"
             if [[ -n "${line2}" ]]; then
@@ -62,7 +62,7 @@ elif [[ $remote_url =~ bitbucket ]]; then
     # construct bitbucket urls
     # https://bitbucket.org/<user_or_org>/<repo>/src/<commit_or_branch>/<filename>#lines-<line1>:<line2>
     if [[ -n ${filename} ]]; then
-        url=${url}/src/${commit_hash:-${branch}}/${filename}
+        url=${url}/src/${commit_or_branch}/${filename}
         if [[ -n "${line1}" ]]; then
             url="${url}#lines-${line1}"
             if [[ -n "${line2}" ]]; then