[PATCH v4] receive-pack.c: consolidate find header logic

From: John Cai <johncai86@gmail.com>

There are two functions that have very similar logic of finding a header value. find_commit_header, and find_header. We can conslidate the logic by introducing a new function find_header_mem, which is equivalent to find_commit_header except it takes a len parameter that determines how many bytes will be read. find_commit_header and find_header can then both call find_header_mem.

This reduces duplicate logic, as the logic for finding header values can now all live in one place.

Signed-off-by: John Cai <johncai86@gmail.com>
---
    Consolidate find_header logic into one function
    
    This addresses the NEEDSWORK comment in builtin/receive-pack.c:
    
     /**
       * NEEDSWORK: reuse find_commit_header() from jk/commit-author-parsing
       * after dropping "_commit" from its name and possibly moving it out
       * of commit.c
       **/
    
    
    There are two functions that have very similar logic of finding a header
    value. find_commit_header, and find_header. We can conslidate the logic
    by introducing a new function find_header_mem, which is equivalent to
    find_commit_header except it takes a len parameter that determines how
    many bytes will be read. find_commit_header and find_header can then
    both call find_header_mem.
    
    This reduces duplicate logic, as the logic for finding header values can
    now all live in one place.
    
    Changes since v4:
    
     * added NEEDSWORK block detailing what needs to be done to clean up
       find_header_mem
    
    Changes since v3:
    
     * fixed verbiage in commit message
     * adjusted style of an if block (based on Junio's feedback)

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1125%2Fjohn-cai%2Fjc%2Freplace-find-header-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1125/john-cai/jc/replace-find-header-v4
Pull-Request: https://github.com/git/git/pull/1125

Range-diff vs v3:

 1:  463df42e7e0 ! 1:  a7b00022b00 receive-pack.c: consolidate find header logic
     @@ Commit message
      
          There are two functions that have very similar logic of finding a header
          value. find_commit_header, and find_header. We can conslidate the logic
     -    by using find_commit_header and replacing the logic in find_header.
     -
     -    Introduce a new function find_header_max, which is equivalent to
     +    by introducing a new function find_header_mem, which is equivalent to
          find_commit_header except it takes a len parameter that determines how
     -    many bytes to read. find_commit_header can then call find_header_max
     -    with 0 as the len.
     +    many bytes will be read. find_commit_header and find_header can then both
     +    call find_header_mem.
      
     -    This cleans up duplicate logic, as the logic for finding header values
     -    is now all in one place.
     +    This reduces duplicate logic, as the logic for finding header values
     +    can now all live in one place.
      
          Signed-off-by: John Cai <johncai86@gmail.com>
      
     @@ builtin/receive-pack.c: static char *prepare_push_cert_nonce(const char *path, t
      +	size_t out_len;
      +	const char *val = find_header_mem(msg, len, key, &out_len);
      +
     -+	if (val == NULL)
     ++	if (!val)
      +		return NULL;
      +
      +	if (next_line)
     @@ commit.c: struct commit_list **commit_list_append(struct commit *commit,
       	const char *line = msg;
       
      -	while (line) {
     ++	/*
     ++	 * NEEDSWORK: Between line[0] and msg[len], there may not be a LF nor NUL
     ++	 * at all, and strchrnul() will scan beyond the range we were given
     ++	 * Make this operation safer and abide by the contract to only read up to len.
     ++	 */
      +	while (line && line < msg + len) {
       		const char *eol = strchrnul(line, '\n');
       

 builtin/receive-pack.c | 33 ++++++++++-----------------------
 commit.c               | 14 ++++++++++++--
 commit.h               |  5 +++++
 3 files changed, 27 insertions(+), 25 deletions(-)